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A Comparison of Hospital Length of Stay and Short-term Morbidity Between the Anterior and the Posterior Approaches to Total Hip Arthroplasty
The Journal of Arthroplasty 28 (2013) 849–854
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A Comparison of Hospital Length of Stay and Short-term Morbidity Between the Anterior and the Posterior Approaches to Total Hip Arthroplasty Christopher T. Martin MD, Andrew J. Pugely MD, Yubo Gao PhD, Charles R. Clark MD The Department of Orthopaedic Surgery and Rehabilitation, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, 01008 JPP, Iowa City, IA, USA
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Article history: Received 24 July 2012 Accepted 29 October 2012 Keywords: anterior approach posterior approach total hip arthroplasty hospital length of stay discharge
a b s t r a c t The efficacy of the anterior, relative to other operative approaches, in promoting earlier return to function after hip arthroplasty has not been well established. We retrospectively compared 41 anterior and 47 posterior approach cases. Mean hospital stay (2.9 vs. 4 days, p = 0.001) and days to mobilization (2.4 vs. 3.2 days, p = 0.006) were shorter with the anterior approach. After multivariate regression, the anterior approach remained a significant predictor of early discharge (p = 0.009). Lateral femoral cutaneous nerve neuropraxia (17%) and fracture (2%), were more common in the anterior cohort, but all patients recovered without sequela. Overall, the anterior approach patients had earlier discharge and mobilization as compared to patients who received the posterior approach. Neuropraxia and fracture remain a concern, but the clinical significance was low in our cohort. © 2013 Elsevier Inc. All rights reserved.
In recent years, increasing attention has been placed on alternative, less invasive approaches to total hip arthroplasty [1–3]. Of the multitude of approaches available, the anterior approach is the only to make use of a true inter-muscular and inter-nervous interval [2,4]. The muscle- and nerve-sparing nature of the approach presumably allows for very rapid post-operative recovery. Several large case series have shown the anterior approach to have a low dislocation rate and early return to ambulation [5–9]. However, questions remain regarding the relative safety of the anterior approach, as complications such as lateral femoral cutaneous nerve neuropraxia remain high [10,11], particularly in the first 100 cases of a surgeon's experience [5,12]. Furthermore, few studies have directly compared the anterior approach with an alternative method [13–15]. Thus, it is yet to be determined if the anterior approach successfully achieves the goal of improved post-operative recovery, relative to other approaches with similar post-operative protocols. In this study, our goal was to compare the short-term perioperative outcomes of the anterior and posterior approaches to total hip arthroplasty, in a series performed by a single surgeon at a single institution. We hypothesized that the anterior approach would allow
This study was approved by the institutional review board at the University of Iowa. There was no external source of funding for this study. All authors listed have reviewed the manuscript, contributed substantively to the manuscript, and agree with its content. The Conflict of Interest statement associated with this article can be found at http:// dx.doi.org/10.1016/j.arth.2012.10.029. Reprint requests: Christopher T. Martin, MD, Department of Orthopaedic Surgery, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, 01008 JPP, Iowa City, IA 52242, USA. 0883-5403/2805-0027$36.00/0 – see front matter © 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.arth.2012.10.029
for earlier hospital discharge, without a significant increase in the risk of peri-operative complications. Materials and Methods Data Review This study obtained IRB approval. Our institution maintains a prospectively collected electronic database of patient records. The CPT codes for primary total hip arthroplasty were used to query this database for cases completed between 2005 and 2010 and identify our patient cohort. We included a consecutive series of 88 cases in 82 patients who underwent an elective primary total hip arthroplasty performed by a single surgeon (CRC), and who completed at least 6month follow-up. We excluded patients who had bilateral procedures on the same day. At pre-operative visits patients were asked to complete a survey in order to provide baseline demographic information (age, race, marital status, self-reported tobacco and alcohol use, self-reported diabetes status, other medical comorbidities, SF36 score, and WOMAC scores). Post-operatively, we asked patients to follow up at 6 weeks and again at 6 months, where SF36 and WOMAC surveys, as well as AP pelvic radiographs were again obtained. Post-operative progress notes, discharge summaries, and clinic visits up to 6 months post-operatively were reviewed to identify the incidence of post-operative complications. Operative blood loss and the incidence of packed red blood cell (PRBC) transfusion were identified from a review of the operative note, the anesthesia report, and nursing documentation. The surveys are optional and 1 patient declined to provide a response for race, 4 declined for alcohol use, and 13 declined for diabetes status.
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Transfusion and operative blood loss data were missing for two and three patients respectively. We had complete data for all other responses. The patients were divided into treatment groups based on the type of surgical approach, with 41 cases in the anterior approach group and 47 in the posterior approach group. Radiographic Measurements Each 6-week post-operative radiograph was measured for cup inclination angle [16], cup anteversion angle [5,16], coronal plane stem alignment, femoral head offset discrepancy, and leg length discrepancy. Leg length discrepancy was also measured immediately post-operatively from low AP radiographs taken in the recovery room. Coronal plane stem alignment was similar to the method used by Nakata et al. [14]. Leg length discrepancy was determined by measuring in millimeters the difference between the transischial line and a line between the lesser trochanters bilaterally, and then comparing the difference between the operative side and the contralateral side. Femoral head offset discrepancy was determined by drawing a line parallel to the femoral shaft, measuring the distance from that line to the center of the femoral head, and comparing the difference between the operated and non-operative side. In order to account for magnification, we measured the diameter of the femoral head and then compared this to the actual size of the femoral head documented in the operative note. A correction factor was obtained by dividing the measured size of the head into the true size, and multiplied through our measurements to account for the magnification. Each radiograph was measured separately by two orthopedic surgery residents (CTM and AJP), who were blinded to the approach used in the operation. Our numbers are reported as the averages of their two measurements. Inter-observer correlation coefficients (ICC) are reported, with b 0.40 considered poor, 0.40– 0.75 considered good, and N 0.75 considered excellent [17,18]. Three patients were missing at least one radiographic measurement due to inability to obtain the radiograph. All other patients had complete radiographic data. Surgical Technique The surgeries were all completed by the senior author (CRC) using either a standard anterior approach, or a standard posterior approach. The surgical approach for the anterior [4,9,19] and posterior [4,20] techniques has been described in detail elsewhere. Our techniques are consistent with these widely used approaches. A brief description of the two approaches is provided below. The anterior approach was started by placing the patient in the supine position on a HANA® (Mizuho OSI, Union City, CA) operative table. The incision was started approximately three finger-breadths lateral to the anterior–superior iliac spine (ASIS) and extended in an oblique fashion for roughly 10 cm. The estimated length of the incision was recorded for each procedure. After exposure of the femoral head, gross traction was applied, and the hip was dislocated using manual traction and 100° of external rotation. The femoral neck was then osteotomized and removed, and the cup was reamed to an appropriate size before impaction of the acetabular implant. For femoral preparation, the table was placed into trendelenburg, a femoral hook was placed, and the leg was extended with the spar brought to the floor. The leg was then adducted and externally rotated to 100° to provide adequate exposure. The knee was palpated through the drapes during this maneuver to insure that motion occurs atraumatically. The femoral canal was then prepared in a standard fashion with the broach, calcar planar, and then insertion of the femoral trial. The hip was then reduced and a fluoroscopic image was taken to verify positioning and leg length. The final components were then placed and the wound was closed in a standard fashion.
The posterior approach was started by placing the patient in the lateral decubitus position on a Capello board (Innomed Inc., Savanna, GA). The incision was centered over the posterior aspect of the greater trochanter, and the estimated length was recorded for each procedure. After a standard exposure and posterior dislocation, the femoral neck was osteotomized and the femoral head was removed using a corkscrew to provide exposure of the acetabulum. The acetabulum was then reamed, and an acetabular prosthesis was impacted. One dome screw was usually used to secure the prosthesis in place. After standard preparation of the femoral canal, trial implants were then placed. Stability was verified by flexing to 90° and internally rotating to 90°. Fluoroscopic images were obtained to verify positioning of the components and leg length. Final implants were then chosen, and the wound closed in a standard fashion. Post-Operative Care Standard post-operative care of the foley catheter, drains, dietary advancement, pain control, and discharge planning was the same for all patients. All patients received elastic compression stockings and pneumatic foot compression boots post-operatively. All patients received physical therapy starting on post-operative day 1. Early mobilization was strongly encouraged, and our physical therapists assessed daily mobility. The physical therapists were given hip precautions, specific to each approach, to prevent dislocations. The posterior approach patients were instructed not to hyperflex, adduct, and internally rotate the leg. The anterior approach patients were instructed not to hyperextend and externally rotate the leg. Patients were discharged home when their pain was controlled or an oral regimen, they were tolerating a regular diet, and they were deemed safe to go home by the therapist with regard to mobilization. Days to independent mobilization was determined by a review of the daily physical therapy progress notes. Patients were considered independent in mobilization when they could walk independently or when they were deemed safe for discharge to home by the physical therapist. Eight patients did not achieve independent mobilization during their hospital stay and were discharged to a rehab or skilled nursing facility. Thus their time to independent mobilization is unknown, and these eight patients were not included in the time to mobilization analysis. Statistical Analysis Categorical variables were analyzed using a standard chi-squared analysis (gender, incidence of any complication) or Fisher's exact test (discharge disposition, race, smoking history, diabetes, indication for surgery, alcohol history, incidence of individual complications), depending on the cell counts. Continuous variables (SF36 and WOMAC scores, length of hospitalization, operative blood loss, units of PRBC transfused, reduction in Hg in the first 24 h, ASA class, total number of medical comorbidities, age, BMI, and operative time) were analyzed with a Student's t test. For simplicity of reporting, our WOMAC surveys are scaled out of 100, with 100 being the best possible score. To account for differences in patient factors between cohorts, we conducted a multivariate regression analysis. The independent variables were age, gender, diabetes, total number of medical comorbidities, ASA class, SF36 pre-operative mental function, SF36 preoperative physical function, smoking history response of “current smoker,” operative approach, estimated operative blood loss, BMI, and units of PRBC transfused. The dependent variable was hospital length of stay (LOS). Hospital LOS is a right skewed data set. Multivariate analyses require a normally distributed dependent variable. Thus, we applied a logarithmic correction to the hospital LOS in order to
C.T. Martin et al. / The Journal of Arthroplasty 28 (2013) 849–854
convert it to a normal distribution. A p value b 0.05 was considered significant in each analysis.
Table 2 Peri-operative Outcomes. Characteristica
Results The mean body mass index (BMI) was higher in the posterior approach group (34.1 vs. 28.5 kg/m [2], p b 0.0001). The mean age was significantly higher in the anterior approach group (63 vs. 57 years, p = 0.02). The posterior cohort had a small, but statistically significantly higher mean ASA class (2.3 vs. 2.1, p = 0.035). There were no other significant differences in demographics or medical comorbidities across groups, and the indications were similar (Table 1). The mean hospital LOS (2.9 vs. 4 days, p = 0.001), mean length of incision (11.0 cm vs. 19.2 cm, p b 0.0001), and mean time to independent mobilization (2.4 vs. 3.2 days, p = 0.006), were all shorter with the anterior approach. The mean operative time was longer with the anterior approach (141 vs. 114 min, p b 0.0001). However, there was no difference across groups in discharge disposition, estimated blood loss, transfusion rate, or reduction in Hg in the first 24 h (Table 2). Twenty-three (56%) of 41 cases in the anterior group and 21 (45%) of 47 cases in the posterior group had at least one complication postoperatively, and this difference was not statistically significant (p = 0.29) (Table 2). However, lateral femoral cutaneous nerve (LFCN) neuropraxia occurred in seven (17%) in the anterior group and zero in the posterior group (p = 0.0035). All patients eventually had complete resolution of their symptoms, and the time to resolution was 6 months in two patients, 9 months in one patient, 10 months in one patient, and 1 year in two patients. The seventh patient was lost to follow-up after the 6-week clinic visit, but when seen again in clinic at 5 years post-operative, the LFCN neuropraxia had completely resolved at that time. Furthermore, one patient in the anterior group
Table 1 Patient Demographics. Characteristic Age (years) BMI (kg/m2) Gender (% female) ASA class Diabetes (%)a Total number of other medical comorbidities Racea Caucasian African American Other Smokinga Current smoker Quit b 6 months ago Quit N 6 months ago Never smoked Alcohol usea None Occasional Regular Surgical indications OA DDH Fracture AVN SCFE FAI Septic arthritis
Anterior Approach
Posterior Approach
p Value
63 (10.6) 28.5 (5.6) 65 2.1 (0.5) 0 3.14 (2.3)
57 (11.9) 34.1 (5.9) 55 2.3 (0.6) 10 3.6 (2.6)
0.02 b 0.0001 0.31 0.035 0.11 0.4
37 0 3
46 1 0
3 1 15 22
12 0 12 23
0.06
0.07
0.054 9 25 4
22 19 5 0.07
36 1 0 4 0 0 0
28 4 1 10 2 1 1
AVN = avascular necrosis, BMI = body mass index, DDH = developmental dysplasia of the hip, FAI = femoral acetabular impingement, OA = primary osteoarthritis, SCFE = slipped capital femoral epiphyses. Bolded values indicate statistical significance (p b 0.05). a Thirteen patients declined to give a response for diabetes status, one declined for race, and four declined for alcohol use.
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Anterior Approach Posterior Approach
Days to independent mobilizationb Hospital length of stay (days) Length of incision (cm) Operative time (min) Operative blood loss (cc)b Units of PRBC transfusedb Reduction in Hg in first 24 h Discharge disposition Home Home with home healthcare Skilled care facility Other Incidence of any complication UTI LFCN neuropraxia Superficial wound infection Trochanteric bursitis Dislocation Post-operative limb length discrepancy Intra-operative fracture
p Value
2.4 (0.72)
3.2 (1.5)
0.006
2.9 (1.1) 11.0 (0.5) 141 (22) 388 (182) 0.28 (0.8) 3.0 (0.89)
4 (1.9) 19.2 (2.8) 114 (22) 423 (253) 0.37 (0.85) 3.7 (0.85)
0.001 b 0.0001 b 0.0001 0.46 0.59 0.59 0.88
37 2 2 0 23 (56%) 9 (22%) 7 (17%) 3 (7%) 3 (7%) 1 (2%) 1 (2%)
38 3 4 2 21 (45%) 7 (15%) 0 (0%) 4 (9%) 7 (15%) 3 (6%) 1 (2%)
1 (2%)
0 (0%)
0.29 0.39 0.0035 1 0.33 0.62 1 0.47
Hg = hemoglobin, LFCN = lateral femoral cutaneous nerve, PRBC = packed red blood cells, UTI = urinary tract infection. Bolded values indicate statistical significance (p b 0.05). a Numbers presented as mean (standard deviation). b Data were not available for eight patients in the days to independent mobilization analysis, two patients for units of PRBC transfused, and three patients for operative blood loss.
sustained an iatrogenic, non-displaced, intra-operative greater trochanteric fracture that was repaired with in situ suture, whereas no intra-operative fractures occurred in the posterior group (p = 0.47). The patient was fully ambulatory post-operatively, and no residual deficits were noted at either the 6-week or the 6-month follow-up visits. One patient in the anterior group and one patient in the posterior group developed clinically noticeable limb length discrepancies post-operatively. The patient in the anterior group developed a fracture of the calcar and 1 cm of subsidence of the component after discharge from the hospital. She was treated with protected weight
Table 3 Radiographic Measurements. Measurementa Leg length discrepancy post-op (mm) Leg length discrepancy 6-week F-U (mm) Acetabular abduction angle (degrees) Acetabular version angle (degrees) Coronal plane alignment (degrees) Femoral head offset discrepancy (mm)
Anterior Approachb
Posterior Approachb
4.5 (3.5)
5.8 (4.4)
0.12
4.8 (4.0)
5.5 (4.6)
0.45
42.2 (3.9)
41.9 (6.2)
0.81
28.5 (7.5)
28 (9.4)
0.80
1.1 (1.2)
0.7 (0.9)
0.07
7.1 (5.2)
7.2 (4.9)
0.89
ICC measurements Leg length discrepancy post-op Leg length discrepancy 6-week F-U Acetabular abduction angle Acetabular version angle Coronal plane alignment Femoral head offset operated side Femoral head offset non operated side
p Value
ICC 0.42 0.65 0.76 0.96 0.7 0.94 0.94
F-U = follow-up, post-op= post-operative, ICC = inter-observer correlation coefficient, which is based on the formula ICC(3,1) [18]. a Radiographic data were missing for three patients. b Numbers are presented as mean (standard deviation).
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Table 4 Outcome Scores. Anterior Approach SF36a Pre-op MCS Pre-op PCS Post-op MCS Post-op PCS Change in MCS Change in PCS WOMACa Pre-op stiffness Pre-op function Pre-op pain Post-op stiffness Post-op function Post-op pain Change in stiffness Change in function Change in pain
Posterior Approach
p Value
49.8 (12.4) 33.4 (8.2) 51.8 (9.7) 45.3 (12) 1.9 (8.4) 11.9 (11.3)
48.4 30.8 49.2 41.3 0.8 10.6
(10.2) (8.1) (11.1) (11.3) (11.6) (11)
0.54 0.13 0.25 0.11 0.59 0.58
46 (21.5) 49.2 (20.7) 50.2 (18.8) 61.6 (26.1) 74.2 (25.7) 90.2 (15.9) 15.6 (25.3) 24.9 (21.4) 40.1 (20.7)
43.9 46.2 45.3 68.9 76.1 86.4 25 29.8 41.2
(24.3) (22.2) (24.2) (19.3) (20.3) (17) (24.9) (24.3) (26.4)
0.66 0.52 0.3 0.14 0.7 0.29 0.08 0.32 0.82
Pre-op = pre-operative, Post-op = post-operative, MCS = Mental Component Score, PCS = Physical Component Score. a Numbers presented as mean (standard deviation).
bearing and a shoe lift, and ambulated well at her final follow-up. The patient in the posterior group had a 1-cm limb length discrepancy immediately post-operatively. This was treated with a shoe lift with good results. Of the eight patients who did not reach independent mobilization, six underwent the posterior approach and two underwent the anterior approach. The BMI in this group averaged 35.9 (range of 19.4–44.1). The operative time averaged 1 h 59 min (range of 1:34 to 2:38). The average age was 65.7 years (range of 44–82 years). The average hospital stay was 5.3 days (range of 3–10 days). The indication for surgery was osteoarthritis in seven patients and AVN in one patient. Three (37.5%) of the eight required a blood transfusion. Six of the eight patients in this cohort had a total of seven minor complications, with four cases of greater trochanteric bursitis, two UTIs, and one of the anterior approach patients who developed a temporary LFCN neuropraxia. There was no significant difference in implant positioning for any of the measured radiographic data points (Table 3). The ICC ranged from good to excellent for inter-observer reliability. There was no difference in SF36 or WOMAC outcomes scores in any category, either pre- or post-operatively (Table 4). Furthermore, although both groups showed an improvement in survey scores from pre- to post-operative, there was no difference in the magnitude of change across groups, in any category. After a multivariate regression analysis, both the type of operative approach (p = 0.009) and units of packed red blood cells transfused (p = 0.015) were independent predictors of hospital LOS. Discussion The anterior approach to total hip arthroplasty has received increased interest in recent years. The muscle-sparing nature of this approach offers the promise of faster recovery times. Furthermore, the reported decreased hospital LOS is a potential source of cost savings in an increasingly price-sensitive health system. However, few studies have investigated its efficacy relative to other approaches. Thus, here we set out to determine if differences existed in peri-operative and short-term outcomes between the anterior and the traditional posterior approaches to total hip arthroplasty. The efficacy of the anterior approach in reducing hospital LOS has been a particular point of interest. Presumably, the muscle-sparing nature of the approach should allow for faster post-operative recovery times. One prior clinical series did report an 8-day reduction in average hospital LOS with the anterior approach as compared to the posterior [14]. However, that study was from Japan, and used a
standard hospital LOS of 30 days for the posterior approach, which is extremely unusual in the United States. Furthermore, studies from the basic science literature have been mixed as to the efficacy of the anterior approach in minimizing muscle damage. Bergin et al. [13] compared elevation in serum markers of muscle damage between the anterior approach and the posterior approach to THA, and found no difference. In contrast, Bremer et al. [21] reported that less soft tissue damage was seen on MRI in patients who underwent the anterior approach, as compared to patients who underwent the posterior approach. Here, we have reported that patients who underwent the anterior approach had a mean hospital LOS that was 1.1 days shorter than patients who underwent the posterior approach (p = 0.001), with the same post-operative protocol. The mean time to independent mobilization was also 0.8 days shorter (p = 0.006). Furthermore, the operative approach was an independent predictor of hospital LOS in a multivariate regression analysis (p = 0.009). Overall, we believe that the anterior approach was successful in promoting early return to function and hospital discharge, relative to the posterior approach. In our experience, the patients who received the anterior approach reported less pain, and therefore we believe that the muscle-sparing nature of the anterior approach was the most notable factor contributing to their more rapid discharge. Eight patients in our study did not reach independent mobilization during their hospitalization. Interestingly, three of those patients required a blood transfusion. In our multivariate analysis, units of PRBC transfused was an independent predictor of hospital LOS (p = 0.015). Furthermore, the BMI was slightly higher in this group, and the patients had a high rate of minor complications. Thus, the failure to mobilize in this cohort is likely a combination of these factors, and our multivariate analysis would seem to indicate that the need for blood transfusion in this cohort was the most significant factor. Allogenic blood transfusion is known to have immunomodulatory effects, and several large studies have shown that it increases the risk of post-operative infection [22,23]. Two of these patients did develop UTI, which is higher than expected. Overall, the role that blood transfusion may have played in prolonging this group's hospital LOS is not clear, but is an interesting area for further study. The most commonly reported drawbacks to the anterior approach are its long operative time, high rate of LFCN neuropraxia, and risk of iatrogenic fracture [11,24]. In this study, the operative times averaged 27 min longer with the anterior approach, and rates of LFCN neuropraxia and iatrogenic fracture in our study were 17% and 2% respectively, which are consistent with previously reported rates [5,11,24]. The patients with LFCN neuropraxia all completely recovered and the patient with an iatrogenic fracture had no appreciable clinical sequela. Furthermore, there was no difference in rates of PRBC transfusion, reduction in Hg in the first 24 h, or overall complication rate. Thus, we believe that the risks associated with the anterior approach to total hip arthroplasty are similar to that of the posterior approach. Although LFCN neuropraxia and iatrogenic fracture may occur, the clinical significance of these complications in our patients was low, as none developed functional limitations. The risk of iatrogenic fracture can be further minimized by placing a hand on the knee as it is externally rotated to dislocate the femoral head, thus ensuring that undue torque is not being applied to the femur. Further, no attempt should be made to start broaching the femur until it is adequately mobilized. Some authors have expressed concern regarding the ability of a surgeon to obtain proper implant positioning through a smaller incision [2]. However, the majority of prior studies on the anterior approach have reported satisfactory implant positioning [5,15], and the one prior study that compared the anterior with the posterior approach showed no significant difference in implant position [14]. Consistent with those prior studies, we found no significant differences across groups between any of the measured radiographic outcomes. We believe that our anterior approach provided adequate
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exposure and satisfactory implant positioning relative to the results achieved through the posterior approach. The majority of prior reports on the anterior approach did not include patient-reported SF36 or WOMAC outcomes data [5,14,15]. One prior study reported improved SF36 outcomes with the anterior approach, as compared to the direct lateral approach, at 6-month follow-up [25]. However, most other studies found no difference between approaches in terms of any patient-reported outcome [2,26]. In our study, patients in both groups demonstrated improvement between pre- and post-operative functional surveys, indicating that both groups had substantial benefit from the operation. However, there was no difference in the magnitude of improvement between groups. Furthermore, the anterior and posterior groups were comparable at both the pre- and post-operative time points. We believe that patient-reported outcomes and satisfaction are similar between the anterior and the posterior approaches, with both groups having excellent results in short-term follow-up. Given the intense cost pressures faced by currently practicing surgeons, it may be reasonable to consider the difference in cost between the two approaches. At our institution, the cost of operative time is billed at $69.00 per minute, and thus the 27 extra minutes of OR time would cost roughly $1863. The daily charge for additional inpatient accommodation is $1560 for acute care and $2510 for intermediate care. In addition the daily charges for extra drugs, dressings, and so on run approximately $500–$700. So the minimum for a typical extra inpatient day would cost just over $2000. Therefore, the cost difference between the extra operative time and the extra day in the hospital is essentially negligible. The specialty equipment we used includes the Hana bed for the anterior approach, which costs in excess of $100,000, versus the Capello board for the posterior approach, which costs roughly $3000. Thus, a considerable investment in specialty equipment may be required to perform the anterior approach for THA. The Hana bed can also be used in fracture care, and this may help to offset the upfront cost. Each institution should understand these costs and analyze hospital volume to determine the feasibility of an investment in new equipment. Our study has several weaknesses. Notably, the BMI is significantly different between the two groups. During consent for the procedure the senior author had a frank discussion about risks and benefits of each approach. The anterior approach was noted to be more technically demanding in obese patients, and in general, the obese patients selected the posterior approach for their procedure as a result of this recommendation (BMI 28.5 vs. 34.1, p b 0.001). It is possible that obese patients are more deconditioned to begin with, leading to longer hospital stays post-operatively, and that this alone explains the difference in hospital discharge between the two approaches. However, we did attempt to control for confounders by conducting a multivariate analysis, and the anterior approach remained an independent predictor of early discharge. This would seem to indicate that the approach does in fact have significance, in spite of the difference in BMI between cohorts. However, further study is still needed to clarify this issue. Ideally, a prospective randomized trial would be conducted, which would minimize the risk of selection bias. Other weaknesses are also deserving of discussion. First, our study is retrospective in nature, and thus we are limited by the completeness and accuracy of the charting that occurred at the initial clinic visits. Second, our study is potentially weakened by selection bias. In addition to BMI which was discussed above, mean age and ASA class were also statistically different. However, the absolute difference in these two values was small, and we do not feel that they are large enough to have clinical significance. There was also a trend toward patients with AVN or DDH undergoing the posterior approach, but this did not reach statistical significance (p = 0.07). Third, radiographic measurements are subjective. We attempted to control for this by having two separate reviewers repeat the measurements, and have reported inter-observer correlations ranging from good to excellent. Fourth, with our study
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numbers we are not powered to detect small differences in some outcomes, and thus it is possible some of our comparisons would become statistically significant with a larger cohort. However, we feel that the clinical significance of those small differences would likely be low, and investigating those outcomes was not the purpose of this study. Fifth, diabetes, smoking, and alcohol use were self-reported on our patient surveys. Self-reporting likely under-represents the true incidence due to patient concern over being stigmatized, and it is not known if willingness to report varied between groups. Lastly, the purpose of this study was to examine differences in short-term outcomes, specifically differences in hospital length of stay and time to independent mobilization. Thus we limited our follow-up to 6 months. Long-term outcomes tend to focus on SF36, WOMAC, and radiographic measures. These outcomes were similar between our groups at a minimum of 6-months follow-up, and thus we suspect that there is little long-term difference in outcomes between these approaches. However, further study will be necessary to determine if any significant differences exist at long-term follow-up points. Overall, we found that patients who received the anterior approach had shorter hospital LOS and earlier mobilization as compared to patients who received the posterior approach, with no significant difference in overall complication rates, risk of transfusion, radiographic outcomes, SF36 or WOMAC scores. Iatrogenic LFCN neuropraxia and intra-operative fracture, however, remain a concern with this approach, and should be discussed with the patient during the consent process. References 1. Hungerford DS. Minimally invasive total hip arthroplasty: in opposition. J Arthroplasty 2004;19(4 Suppl 1):81. 2. Vail TP, Callaghan JJ. Minimal incision total hip arthroplasty. J Am Acad Orthop Surg 2007;15(12):707. 3. Duwelius PJ, Dorr LD. Minimally invasive total hip arthroplasty: an overview of the results. Instr Course Lect 2008;57:215. 4. Hoppenfeld S, DeBoer P, Buckley R. Surgical exposures in orthopaedics: the anatomic approach. Philadelphia, PA: Lippincott Williams & Wilkins; 2009. 5. Matta JM, Shahrdar C, Ferguson T. Single-incision anterior approach for total hip arthroplasty on an orthopaedic table. Clin Orthop Relat Res 2005;441:115. 6. Kennon RE, Keggi JM, Wetmore RS, et al. Total hip arthroplasty through a minimally invasive anterior surgical approach. J Bone Joint Surg Am 2003;85-A(Suppl 4):39. 7. Sariali E, Leonard P, Mamoudy P. Dislocation after total hip arthroplasty using Hueter anterior approach. J Arthroplasty 2008;23(2):266. 8. Bhandari M, Matta JM, Dodgin D, et al. Outcomes following the single-incision anterior approach to total hip arthroplasty: a multicenter observational study. Orthop Clin North Am 2009;40(3):329. 9. Siguier T, Siguier M, Brumpt B. Mini-incision anterior approach does not increase dislocation rate: a study of 1037 total hip replacements. Clin Orthop Relat Res 2004(426):164. 10. Smith TO, Blake V, Hing CB. Minimally invasive versus conventional exposure for total hip arthroplasty: a systematic review and meta-analysis of clinical and radiological outcomes. Int Orthop 2011;35(2):173. 11. Bhargava T, Goytia RN, Jones LC, et al. Lateral femoral cutaneous nerve impairment after direct anterior approach for total hip arthroplasty. Orthopedics 2010;33(7):472. 12. Mast NH, Laude F. Revision total hip arthroplasty performed through the Hueter interval. J Bone Joint Surg Am 2011;93(Suppl 2):143. 13. Bergin PF, Doppelt JD, Kephart CJ, et al. Comparison of minimally invasive direct anterior versus posterior total hip arthroplasty based on inflammation and muscle damage markers. J Bone Joint Surg Am 2011;93(15):1392. 14. Nakata K, Nishikawa M, Yamamoto K, et al. A clinical comparative study of the direct anterior with mini-posterior approach: two consecutive series. J Arthroplasty 2009;24(5):698. 15. Sendtner E, Borowiak K, Schuster T, et al. Tackling the learning curve: comparison between the anterior, minimally invasive (Micro-hip(R)) and the lateral, transgluteal (Bauer) approach for primary total hip replacement. Arch Orthop Trauma Surg 2011;131(5):597. 16. Lewinnek GE, Lewis JL, Tarr R, et al. Dislocations after total hip-replacement arthroplasties. J Bone Joint Surg Am 1978;60(2):217. 17. Shoukri MM, Pause CA. Statistical methods for health sciences. Boca Raton, FL: CRC Press; 1998. 18. Shrout PE, Fleiss JL. Intraclass correlations: uses in assessing rater reliability. Psychol Bull 1979;86(2):420. 19. Bender B, Nogler M, Hozack WJ. Direct anterior approach for total hip arthroplasty. Orthop Clin North Am 2009;40(3):321. 20. Moore AT. The self-locking metal hip prosthesis. J Bone Joint Surg Am 1957;39A(4):811.
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21. Bremer AK, Kalberer F, Pfirrmann CW, et al. Soft-tissue changes in hip abductor muscles and tendons after total hip replacement: comparison between the direct anterior and the transgluteal approaches. J Bone Joint Surg Br 2011;93(7):886. 22. Carson JL, Altman DG, Duff A, et al. Risk of bacterial infection associated with allogeneic blood transfusion among patients undergoing hip fracture repair. Transfusion 1999;39(7):694. 23. Bierbaum BE, Callaghan JJ, Galante JO, et al. An analysis of blood management in patients having a total hip or knee arthroplasty. J Bone Joint Surg Am 1999;81(1):2.
24. Seng BE, Berend KR, Ajluni AF, et al. Anterior-supine minimally invasive total hip arthroplasty: defining the learning curve. Orthop Clin North Am 2009; 40(3):343. 25. Restrepo C, Parvizi J, Pour AE, et al. Prospective randomized study of two surgical approaches for total hip arthroplasty. J Arthroplasty 2010;25(5):671 e1. 26. Meneghini RM, Smits SA. Early discharge and recovery with three minimally invasive total hip arthroplasty approaches: a preliminary study. Clin Orthop Relat Res 2009;467(6):1431.
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The Journal of Arthroplasty journal homepage: www.arthroplastyjournal.org
A Comparison of Hospital Length of Stay and Short-term Morbidity Between the Anterior and the Posterior Approaches to Total Hip Arthroplasty Christopher T. Martin MD, Andrew J. Pugely MD, Yubo Gao PhD, Charles R. Clark MD The Department of Orthopaedic Surgery and Rehabilitation, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, 01008 JPP, Iowa City, IA, USA
a r t i c l e
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Article history: Received 24 July 2012 Accepted 29 October 2012 Keywords: anterior approach posterior approach total hip arthroplasty hospital length of stay discharge
a b s t r a c t The efficacy of the anterior, relative to other operative approaches, in promoting earlier return to function after hip arthroplasty has not been well established. We retrospectively compared 41 anterior and 47 posterior approach cases. Mean hospital stay (2.9 vs. 4 days, p = 0.001) and days to mobilization (2.4 vs. 3.2 days, p = 0.006) were shorter with the anterior approach. After multivariate regression, the anterior approach remained a significant predictor of early discharge (p = 0.009). Lateral femoral cutaneous nerve neuropraxia (17%) and fracture (2%), were more common in the anterior cohort, but all patients recovered without sequela. Overall, the anterior approach patients had earlier discharge and mobilization as compared to patients who received the posterior approach. Neuropraxia and fracture remain a concern, but the clinical significance was low in our cohort. © 2013 Elsevier Inc. All rights reserved.
In recent years, increasing attention has been placed on alternative, less invasive approaches to total hip arthroplasty [1–3]. Of the multitude of approaches available, the anterior approach is the only to make use of a true inter-muscular and inter-nervous interval [2,4]. The muscle- and nerve-sparing nature of the approach presumably allows for very rapid post-operative recovery. Several large case series have shown the anterior approach to have a low dislocation rate and early return to ambulation [5–9]. However, questions remain regarding the relative safety of the anterior approach, as complications such as lateral femoral cutaneous nerve neuropraxia remain high [10,11], particularly in the first 100 cases of a surgeon's experience [5,12]. Furthermore, few studies have directly compared the anterior approach with an alternative method [13–15]. Thus, it is yet to be determined if the anterior approach successfully achieves the goal of improved post-operative recovery, relative to other approaches with similar post-operative protocols. In this study, our goal was to compare the short-term perioperative outcomes of the anterior and posterior approaches to total hip arthroplasty, in a series performed by a single surgeon at a single institution. We hypothesized that the anterior approach would allow
This study was approved by the institutional review board at the University of Iowa. There was no external source of funding for this study. All authors listed have reviewed the manuscript, contributed substantively to the manuscript, and agree with its content. The Conflict of Interest statement associated with this article can be found at http:// dx.doi.org/10.1016/j.arth.2012.10.029. Reprint requests: Christopher T. Martin, MD, Department of Orthopaedic Surgery, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, 01008 JPP, Iowa City, IA 52242, USA. 0883-5403/2805-0027$36.00/0 – see front matter © 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.arth.2012.10.029
for earlier hospital discharge, without a significant increase in the risk of peri-operative complications. Materials and Methods Data Review This study obtained IRB approval. Our institution maintains a prospectively collected electronic database of patient records. The CPT codes for primary total hip arthroplasty were used to query this database for cases completed between 2005 and 2010 and identify our patient cohort. We included a consecutive series of 88 cases in 82 patients who underwent an elective primary total hip arthroplasty performed by a single surgeon (CRC), and who completed at least 6month follow-up. We excluded patients who had bilateral procedures on the same day. At pre-operative visits patients were asked to complete a survey in order to provide baseline demographic information (age, race, marital status, self-reported tobacco and alcohol use, self-reported diabetes status, other medical comorbidities, SF36 score, and WOMAC scores). Post-operatively, we asked patients to follow up at 6 weeks and again at 6 months, where SF36 and WOMAC surveys, as well as AP pelvic radiographs were again obtained. Post-operative progress notes, discharge summaries, and clinic visits up to 6 months post-operatively were reviewed to identify the incidence of post-operative complications. Operative blood loss and the incidence of packed red blood cell (PRBC) transfusion were identified from a review of the operative note, the anesthesia report, and nursing documentation. The surveys are optional and 1 patient declined to provide a response for race, 4 declined for alcohol use, and 13 declined for diabetes status.
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Transfusion and operative blood loss data were missing for two and three patients respectively. We had complete data for all other responses. The patients were divided into treatment groups based on the type of surgical approach, with 41 cases in the anterior approach group and 47 in the posterior approach group. Radiographic Measurements Each 6-week post-operative radiograph was measured for cup inclination angle [16], cup anteversion angle [5,16], coronal plane stem alignment, femoral head offset discrepancy, and leg length discrepancy. Leg length discrepancy was also measured immediately post-operatively from low AP radiographs taken in the recovery room. Coronal plane stem alignment was similar to the method used by Nakata et al. [14]. Leg length discrepancy was determined by measuring in millimeters the difference between the transischial line and a line between the lesser trochanters bilaterally, and then comparing the difference between the operative side and the contralateral side. Femoral head offset discrepancy was determined by drawing a line parallel to the femoral shaft, measuring the distance from that line to the center of the femoral head, and comparing the difference between the operated and non-operative side. In order to account for magnification, we measured the diameter of the femoral head and then compared this to the actual size of the femoral head documented in the operative note. A correction factor was obtained by dividing the measured size of the head into the true size, and multiplied through our measurements to account for the magnification. Each radiograph was measured separately by two orthopedic surgery residents (CTM and AJP), who were blinded to the approach used in the operation. Our numbers are reported as the averages of their two measurements. Inter-observer correlation coefficients (ICC) are reported, with b 0.40 considered poor, 0.40– 0.75 considered good, and N 0.75 considered excellent [17,18]. Three patients were missing at least one radiographic measurement due to inability to obtain the radiograph. All other patients had complete radiographic data. Surgical Technique The surgeries were all completed by the senior author (CRC) using either a standard anterior approach, or a standard posterior approach. The surgical approach for the anterior [4,9,19] and posterior [4,20] techniques has been described in detail elsewhere. Our techniques are consistent with these widely used approaches. A brief description of the two approaches is provided below. The anterior approach was started by placing the patient in the supine position on a HANA® (Mizuho OSI, Union City, CA) operative table. The incision was started approximately three finger-breadths lateral to the anterior–superior iliac spine (ASIS) and extended in an oblique fashion for roughly 10 cm. The estimated length of the incision was recorded for each procedure. After exposure of the femoral head, gross traction was applied, and the hip was dislocated using manual traction and 100° of external rotation. The femoral neck was then osteotomized and removed, and the cup was reamed to an appropriate size before impaction of the acetabular implant. For femoral preparation, the table was placed into trendelenburg, a femoral hook was placed, and the leg was extended with the spar brought to the floor. The leg was then adducted and externally rotated to 100° to provide adequate exposure. The knee was palpated through the drapes during this maneuver to insure that motion occurs atraumatically. The femoral canal was then prepared in a standard fashion with the broach, calcar planar, and then insertion of the femoral trial. The hip was then reduced and a fluoroscopic image was taken to verify positioning and leg length. The final components were then placed and the wound was closed in a standard fashion.
The posterior approach was started by placing the patient in the lateral decubitus position on a Capello board (Innomed Inc., Savanna, GA). The incision was centered over the posterior aspect of the greater trochanter, and the estimated length was recorded for each procedure. After a standard exposure and posterior dislocation, the femoral neck was osteotomized and the femoral head was removed using a corkscrew to provide exposure of the acetabulum. The acetabulum was then reamed, and an acetabular prosthesis was impacted. One dome screw was usually used to secure the prosthesis in place. After standard preparation of the femoral canal, trial implants were then placed. Stability was verified by flexing to 90° and internally rotating to 90°. Fluoroscopic images were obtained to verify positioning of the components and leg length. Final implants were then chosen, and the wound closed in a standard fashion. Post-Operative Care Standard post-operative care of the foley catheter, drains, dietary advancement, pain control, and discharge planning was the same for all patients. All patients received elastic compression stockings and pneumatic foot compression boots post-operatively. All patients received physical therapy starting on post-operative day 1. Early mobilization was strongly encouraged, and our physical therapists assessed daily mobility. The physical therapists were given hip precautions, specific to each approach, to prevent dislocations. The posterior approach patients were instructed not to hyperflex, adduct, and internally rotate the leg. The anterior approach patients were instructed not to hyperextend and externally rotate the leg. Patients were discharged home when their pain was controlled or an oral regimen, they were tolerating a regular diet, and they were deemed safe to go home by the therapist with regard to mobilization. Days to independent mobilization was determined by a review of the daily physical therapy progress notes. Patients were considered independent in mobilization when they could walk independently or when they were deemed safe for discharge to home by the physical therapist. Eight patients did not achieve independent mobilization during their hospital stay and were discharged to a rehab or skilled nursing facility. Thus their time to independent mobilization is unknown, and these eight patients were not included in the time to mobilization analysis. Statistical Analysis Categorical variables were analyzed using a standard chi-squared analysis (gender, incidence of any complication) or Fisher's exact test (discharge disposition, race, smoking history, diabetes, indication for surgery, alcohol history, incidence of individual complications), depending on the cell counts. Continuous variables (SF36 and WOMAC scores, length of hospitalization, operative blood loss, units of PRBC transfused, reduction in Hg in the first 24 h, ASA class, total number of medical comorbidities, age, BMI, and operative time) were analyzed with a Student's t test. For simplicity of reporting, our WOMAC surveys are scaled out of 100, with 100 being the best possible score. To account for differences in patient factors between cohorts, we conducted a multivariate regression analysis. The independent variables were age, gender, diabetes, total number of medical comorbidities, ASA class, SF36 pre-operative mental function, SF36 preoperative physical function, smoking history response of “current smoker,” operative approach, estimated operative blood loss, BMI, and units of PRBC transfused. The dependent variable was hospital length of stay (LOS). Hospital LOS is a right skewed data set. Multivariate analyses require a normally distributed dependent variable. Thus, we applied a logarithmic correction to the hospital LOS in order to
C.T. Martin et al. / The Journal of Arthroplasty 28 (2013) 849–854
convert it to a normal distribution. A p value b 0.05 was considered significant in each analysis.
Table 2 Peri-operative Outcomes. Characteristica
Results The mean body mass index (BMI) was higher in the posterior approach group (34.1 vs. 28.5 kg/m [2], p b 0.0001). The mean age was significantly higher in the anterior approach group (63 vs. 57 years, p = 0.02). The posterior cohort had a small, but statistically significantly higher mean ASA class (2.3 vs. 2.1, p = 0.035). There were no other significant differences in demographics or medical comorbidities across groups, and the indications were similar (Table 1). The mean hospital LOS (2.9 vs. 4 days, p = 0.001), mean length of incision (11.0 cm vs. 19.2 cm, p b 0.0001), and mean time to independent mobilization (2.4 vs. 3.2 days, p = 0.006), were all shorter with the anterior approach. The mean operative time was longer with the anterior approach (141 vs. 114 min, p b 0.0001). However, there was no difference across groups in discharge disposition, estimated blood loss, transfusion rate, or reduction in Hg in the first 24 h (Table 2). Twenty-three (56%) of 41 cases in the anterior group and 21 (45%) of 47 cases in the posterior group had at least one complication postoperatively, and this difference was not statistically significant (p = 0.29) (Table 2). However, lateral femoral cutaneous nerve (LFCN) neuropraxia occurred in seven (17%) in the anterior group and zero in the posterior group (p = 0.0035). All patients eventually had complete resolution of their symptoms, and the time to resolution was 6 months in two patients, 9 months in one patient, 10 months in one patient, and 1 year in two patients. The seventh patient was lost to follow-up after the 6-week clinic visit, but when seen again in clinic at 5 years post-operative, the LFCN neuropraxia had completely resolved at that time. Furthermore, one patient in the anterior group
Table 1 Patient Demographics. Characteristic Age (years) BMI (kg/m2) Gender (% female) ASA class Diabetes (%)a Total number of other medical comorbidities Racea Caucasian African American Other Smokinga Current smoker Quit b 6 months ago Quit N 6 months ago Never smoked Alcohol usea None Occasional Regular Surgical indications OA DDH Fracture AVN SCFE FAI Septic arthritis
Anterior Approach
Posterior Approach
p Value
63 (10.6) 28.5 (5.6) 65 2.1 (0.5) 0 3.14 (2.3)
57 (11.9) 34.1 (5.9) 55 2.3 (0.6) 10 3.6 (2.6)
0.02 b 0.0001 0.31 0.035 0.11 0.4
37 0 3
46 1 0
3 1 15 22
12 0 12 23
0.06
0.07
0.054 9 25 4
22 19 5 0.07
36 1 0 4 0 0 0
28 4 1 10 2 1 1
AVN = avascular necrosis, BMI = body mass index, DDH = developmental dysplasia of the hip, FAI = femoral acetabular impingement, OA = primary osteoarthritis, SCFE = slipped capital femoral epiphyses. Bolded values indicate statistical significance (p b 0.05). a Thirteen patients declined to give a response for diabetes status, one declined for race, and four declined for alcohol use.
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Anterior Approach Posterior Approach
Days to independent mobilizationb Hospital length of stay (days) Length of incision (cm) Operative time (min) Operative blood loss (cc)b Units of PRBC transfusedb Reduction in Hg in first 24 h Discharge disposition Home Home with home healthcare Skilled care facility Other Incidence of any complication UTI LFCN neuropraxia Superficial wound infection Trochanteric bursitis Dislocation Post-operative limb length discrepancy Intra-operative fracture
p Value
2.4 (0.72)
3.2 (1.5)
0.006
2.9 (1.1) 11.0 (0.5) 141 (22) 388 (182) 0.28 (0.8) 3.0 (0.89)
4 (1.9) 19.2 (2.8) 114 (22) 423 (253) 0.37 (0.85) 3.7 (0.85)
0.001 b 0.0001 b 0.0001 0.46 0.59 0.59 0.88
37 2 2 0 23 (56%) 9 (22%) 7 (17%) 3 (7%) 3 (7%) 1 (2%) 1 (2%)
38 3 4 2 21 (45%) 7 (15%) 0 (0%) 4 (9%) 7 (15%) 3 (6%) 1 (2%)
1 (2%)
0 (0%)
0.29 0.39 0.0035 1 0.33 0.62 1 0.47
Hg = hemoglobin, LFCN = lateral femoral cutaneous nerve, PRBC = packed red blood cells, UTI = urinary tract infection. Bolded values indicate statistical significance (p b 0.05). a Numbers presented as mean (standard deviation). b Data were not available for eight patients in the days to independent mobilization analysis, two patients for units of PRBC transfused, and three patients for operative blood loss.
sustained an iatrogenic, non-displaced, intra-operative greater trochanteric fracture that was repaired with in situ suture, whereas no intra-operative fractures occurred in the posterior group (p = 0.47). The patient was fully ambulatory post-operatively, and no residual deficits were noted at either the 6-week or the 6-month follow-up visits. One patient in the anterior group and one patient in the posterior group developed clinically noticeable limb length discrepancies post-operatively. The patient in the anterior group developed a fracture of the calcar and 1 cm of subsidence of the component after discharge from the hospital. She was treated with protected weight
Table 3 Radiographic Measurements. Measurementa Leg length discrepancy post-op (mm) Leg length discrepancy 6-week F-U (mm) Acetabular abduction angle (degrees) Acetabular version angle (degrees) Coronal plane alignment (degrees) Femoral head offset discrepancy (mm)
Anterior Approachb
Posterior Approachb
4.5 (3.5)
5.8 (4.4)
0.12
4.8 (4.0)
5.5 (4.6)
0.45
42.2 (3.9)
41.9 (6.2)
0.81
28.5 (7.5)
28 (9.4)
0.80
1.1 (1.2)
0.7 (0.9)
0.07
7.1 (5.2)
7.2 (4.9)
0.89
ICC measurements Leg length discrepancy post-op Leg length discrepancy 6-week F-U Acetabular abduction angle Acetabular version angle Coronal plane alignment Femoral head offset operated side Femoral head offset non operated side
p Value
ICC 0.42 0.65 0.76 0.96 0.7 0.94 0.94
F-U = follow-up, post-op= post-operative, ICC = inter-observer correlation coefficient, which is based on the formula ICC(3,1) [18]. a Radiographic data were missing for three patients. b Numbers are presented as mean (standard deviation).
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Table 4 Outcome Scores. Anterior Approach SF36a Pre-op MCS Pre-op PCS Post-op MCS Post-op PCS Change in MCS Change in PCS WOMACa Pre-op stiffness Pre-op function Pre-op pain Post-op stiffness Post-op function Post-op pain Change in stiffness Change in function Change in pain
Posterior Approach
p Value
49.8 (12.4) 33.4 (8.2) 51.8 (9.7) 45.3 (12) 1.9 (8.4) 11.9 (11.3)
48.4 30.8 49.2 41.3 0.8 10.6
(10.2) (8.1) (11.1) (11.3) (11.6) (11)
0.54 0.13 0.25 0.11 0.59 0.58
46 (21.5) 49.2 (20.7) 50.2 (18.8) 61.6 (26.1) 74.2 (25.7) 90.2 (15.9) 15.6 (25.3) 24.9 (21.4) 40.1 (20.7)
43.9 46.2 45.3 68.9 76.1 86.4 25 29.8 41.2
(24.3) (22.2) (24.2) (19.3) (20.3) (17) (24.9) (24.3) (26.4)
0.66 0.52 0.3 0.14 0.7 0.29 0.08 0.32 0.82
Pre-op = pre-operative, Post-op = post-operative, MCS = Mental Component Score, PCS = Physical Component Score. a Numbers presented as mean (standard deviation).
bearing and a shoe lift, and ambulated well at her final follow-up. The patient in the posterior group had a 1-cm limb length discrepancy immediately post-operatively. This was treated with a shoe lift with good results. Of the eight patients who did not reach independent mobilization, six underwent the posterior approach and two underwent the anterior approach. The BMI in this group averaged 35.9 (range of 19.4–44.1). The operative time averaged 1 h 59 min (range of 1:34 to 2:38). The average age was 65.7 years (range of 44–82 years). The average hospital stay was 5.3 days (range of 3–10 days). The indication for surgery was osteoarthritis in seven patients and AVN in one patient. Three (37.5%) of the eight required a blood transfusion. Six of the eight patients in this cohort had a total of seven minor complications, with four cases of greater trochanteric bursitis, two UTIs, and one of the anterior approach patients who developed a temporary LFCN neuropraxia. There was no significant difference in implant positioning for any of the measured radiographic data points (Table 3). The ICC ranged from good to excellent for inter-observer reliability. There was no difference in SF36 or WOMAC outcomes scores in any category, either pre- or post-operatively (Table 4). Furthermore, although both groups showed an improvement in survey scores from pre- to post-operative, there was no difference in the magnitude of change across groups, in any category. After a multivariate regression analysis, both the type of operative approach (p = 0.009) and units of packed red blood cells transfused (p = 0.015) were independent predictors of hospital LOS. Discussion The anterior approach to total hip arthroplasty has received increased interest in recent years. The muscle-sparing nature of this approach offers the promise of faster recovery times. Furthermore, the reported decreased hospital LOS is a potential source of cost savings in an increasingly price-sensitive health system. However, few studies have investigated its efficacy relative to other approaches. Thus, here we set out to determine if differences existed in peri-operative and short-term outcomes between the anterior and the traditional posterior approaches to total hip arthroplasty. The efficacy of the anterior approach in reducing hospital LOS has been a particular point of interest. Presumably, the muscle-sparing nature of the approach should allow for faster post-operative recovery times. One prior clinical series did report an 8-day reduction in average hospital LOS with the anterior approach as compared to the posterior [14]. However, that study was from Japan, and used a
standard hospital LOS of 30 days for the posterior approach, which is extremely unusual in the United States. Furthermore, studies from the basic science literature have been mixed as to the efficacy of the anterior approach in minimizing muscle damage. Bergin et al. [13] compared elevation in serum markers of muscle damage between the anterior approach and the posterior approach to THA, and found no difference. In contrast, Bremer et al. [21] reported that less soft tissue damage was seen on MRI in patients who underwent the anterior approach, as compared to patients who underwent the posterior approach. Here, we have reported that patients who underwent the anterior approach had a mean hospital LOS that was 1.1 days shorter than patients who underwent the posterior approach (p = 0.001), with the same post-operative protocol. The mean time to independent mobilization was also 0.8 days shorter (p = 0.006). Furthermore, the operative approach was an independent predictor of hospital LOS in a multivariate regression analysis (p = 0.009). Overall, we believe that the anterior approach was successful in promoting early return to function and hospital discharge, relative to the posterior approach. In our experience, the patients who received the anterior approach reported less pain, and therefore we believe that the muscle-sparing nature of the anterior approach was the most notable factor contributing to their more rapid discharge. Eight patients in our study did not reach independent mobilization during their hospitalization. Interestingly, three of those patients required a blood transfusion. In our multivariate analysis, units of PRBC transfused was an independent predictor of hospital LOS (p = 0.015). Furthermore, the BMI was slightly higher in this group, and the patients had a high rate of minor complications. Thus, the failure to mobilize in this cohort is likely a combination of these factors, and our multivariate analysis would seem to indicate that the need for blood transfusion in this cohort was the most significant factor. Allogenic blood transfusion is known to have immunomodulatory effects, and several large studies have shown that it increases the risk of post-operative infection [22,23]. Two of these patients did develop UTI, which is higher than expected. Overall, the role that blood transfusion may have played in prolonging this group's hospital LOS is not clear, but is an interesting area for further study. The most commonly reported drawbacks to the anterior approach are its long operative time, high rate of LFCN neuropraxia, and risk of iatrogenic fracture [11,24]. In this study, the operative times averaged 27 min longer with the anterior approach, and rates of LFCN neuropraxia and iatrogenic fracture in our study were 17% and 2% respectively, which are consistent with previously reported rates [5,11,24]. The patients with LFCN neuropraxia all completely recovered and the patient with an iatrogenic fracture had no appreciable clinical sequela. Furthermore, there was no difference in rates of PRBC transfusion, reduction in Hg in the first 24 h, or overall complication rate. Thus, we believe that the risks associated with the anterior approach to total hip arthroplasty are similar to that of the posterior approach. Although LFCN neuropraxia and iatrogenic fracture may occur, the clinical significance of these complications in our patients was low, as none developed functional limitations. The risk of iatrogenic fracture can be further minimized by placing a hand on the knee as it is externally rotated to dislocate the femoral head, thus ensuring that undue torque is not being applied to the femur. Further, no attempt should be made to start broaching the femur until it is adequately mobilized. Some authors have expressed concern regarding the ability of a surgeon to obtain proper implant positioning through a smaller incision [2]. However, the majority of prior studies on the anterior approach have reported satisfactory implant positioning [5,15], and the one prior study that compared the anterior with the posterior approach showed no significant difference in implant position [14]. Consistent with those prior studies, we found no significant differences across groups between any of the measured radiographic outcomes. We believe that our anterior approach provided adequate
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exposure and satisfactory implant positioning relative to the results achieved through the posterior approach. The majority of prior reports on the anterior approach did not include patient-reported SF36 or WOMAC outcomes data [5,14,15]. One prior study reported improved SF36 outcomes with the anterior approach, as compared to the direct lateral approach, at 6-month follow-up [25]. However, most other studies found no difference between approaches in terms of any patient-reported outcome [2,26]. In our study, patients in both groups demonstrated improvement between pre- and post-operative functional surveys, indicating that both groups had substantial benefit from the operation. However, there was no difference in the magnitude of improvement between groups. Furthermore, the anterior and posterior groups were comparable at both the pre- and post-operative time points. We believe that patient-reported outcomes and satisfaction are similar between the anterior and the posterior approaches, with both groups having excellent results in short-term follow-up. Given the intense cost pressures faced by currently practicing surgeons, it may be reasonable to consider the difference in cost between the two approaches. At our institution, the cost of operative time is billed at $69.00 per minute, and thus the 27 extra minutes of OR time would cost roughly $1863. The daily charge for additional inpatient accommodation is $1560 for acute care and $2510 for intermediate care. In addition the daily charges for extra drugs, dressings, and so on run approximately $500–$700. So the minimum for a typical extra inpatient day would cost just over $2000. Therefore, the cost difference between the extra operative time and the extra day in the hospital is essentially negligible. The specialty equipment we used includes the Hana bed for the anterior approach, which costs in excess of $100,000, versus the Capello board for the posterior approach, which costs roughly $3000. Thus, a considerable investment in specialty equipment may be required to perform the anterior approach for THA. The Hana bed can also be used in fracture care, and this may help to offset the upfront cost. Each institution should understand these costs and analyze hospital volume to determine the feasibility of an investment in new equipment. Our study has several weaknesses. Notably, the BMI is significantly different between the two groups. During consent for the procedure the senior author had a frank discussion about risks and benefits of each approach. The anterior approach was noted to be more technically demanding in obese patients, and in general, the obese patients selected the posterior approach for their procedure as a result of this recommendation (BMI 28.5 vs. 34.1, p b 0.001). It is possible that obese patients are more deconditioned to begin with, leading to longer hospital stays post-operatively, and that this alone explains the difference in hospital discharge between the two approaches. However, we did attempt to control for confounders by conducting a multivariate analysis, and the anterior approach remained an independent predictor of early discharge. This would seem to indicate that the approach does in fact have significance, in spite of the difference in BMI between cohorts. However, further study is still needed to clarify this issue. Ideally, a prospective randomized trial would be conducted, which would minimize the risk of selection bias. Other weaknesses are also deserving of discussion. First, our study is retrospective in nature, and thus we are limited by the completeness and accuracy of the charting that occurred at the initial clinic visits. Second, our study is potentially weakened by selection bias. In addition to BMI which was discussed above, mean age and ASA class were also statistically different. However, the absolute difference in these two values was small, and we do not feel that they are large enough to have clinical significance. There was also a trend toward patients with AVN or DDH undergoing the posterior approach, but this did not reach statistical significance (p = 0.07). Third, radiographic measurements are subjective. We attempted to control for this by having two separate reviewers repeat the measurements, and have reported inter-observer correlations ranging from good to excellent. Fourth, with our study
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numbers we are not powered to detect small differences in some outcomes, and thus it is possible some of our comparisons would become statistically significant with a larger cohort. However, we feel that the clinical significance of those small differences would likely be low, and investigating those outcomes was not the purpose of this study. Fifth, diabetes, smoking, and alcohol use were self-reported on our patient surveys. Self-reporting likely under-represents the true incidence due to patient concern over being stigmatized, and it is not known if willingness to report varied between groups. Lastly, the purpose of this study was to examine differences in short-term outcomes, specifically differences in hospital length of stay and time to independent mobilization. Thus we limited our follow-up to 6 months. Long-term outcomes tend to focus on SF36, WOMAC, and radiographic measures. These outcomes were similar between our groups at a minimum of 6-months follow-up, and thus we suspect that there is little long-term difference in outcomes between these approaches. However, further study will be necessary to determine if any significant differences exist at long-term follow-up points. Overall, we found that patients who received the anterior approach had shorter hospital LOS and earlier mobilization as compared to patients who received the posterior approach, with no significant difference in overall complication rates, risk of transfusion, radiographic outcomes, SF36 or WOMAC scores. Iatrogenic LFCN neuropraxia and intra-operative fracture, however, remain a concern with this approach, and should be discussed with the patient during the consent process. References 1. Hungerford DS. Minimally invasive total hip arthroplasty: in opposition. J Arthroplasty 2004;19(4 Suppl 1):81. 2. Vail TP, Callaghan JJ. Minimal incision total hip arthroplasty. J Am Acad Orthop Surg 2007;15(12):707. 3. Duwelius PJ, Dorr LD. Minimally invasive total hip arthroplasty: an overview of the results. Instr Course Lect 2008;57:215. 4. Hoppenfeld S, DeBoer P, Buckley R. Surgical exposures in orthopaedics: the anatomic approach. Philadelphia, PA: Lippincott Williams & Wilkins; 2009. 5. Matta JM, Shahrdar C, Ferguson T. Single-incision anterior approach for total hip arthroplasty on an orthopaedic table. Clin Orthop Relat Res 2005;441:115. 6. Kennon RE, Keggi JM, Wetmore RS, et al. Total hip arthroplasty through a minimally invasive anterior surgical approach. J Bone Joint Surg Am 2003;85-A(Suppl 4):39. 7. Sariali E, Leonard P, Mamoudy P. Dislocation after total hip arthroplasty using Hueter anterior approach. J Arthroplasty 2008;23(2):266. 8. Bhandari M, Matta JM, Dodgin D, et al. Outcomes following the single-incision anterior approach to total hip arthroplasty: a multicenter observational study. Orthop Clin North Am 2009;40(3):329. 9. Siguier T, Siguier M, Brumpt B. Mini-incision anterior approach does not increase dislocation rate: a study of 1037 total hip replacements. Clin Orthop Relat Res 2004(426):164. 10. Smith TO, Blake V, Hing CB. Minimally invasive versus conventional exposure for total hip arthroplasty: a systematic review and meta-analysis of clinical and radiological outcomes. Int Orthop 2011;35(2):173. 11. Bhargava T, Goytia RN, Jones LC, et al. Lateral femoral cutaneous nerve impairment after direct anterior approach for total hip arthroplasty. Orthopedics 2010;33(7):472. 12. Mast NH, Laude F. Revision total hip arthroplasty performed through the Hueter interval. J Bone Joint Surg Am 2011;93(Suppl 2):143. 13. Bergin PF, Doppelt JD, Kephart CJ, et al. Comparison of minimally invasive direct anterior versus posterior total hip arthroplasty based on inflammation and muscle damage markers. J Bone Joint Surg Am 2011;93(15):1392. 14. Nakata K, Nishikawa M, Yamamoto K, et al. A clinical comparative study of the direct anterior with mini-posterior approach: two consecutive series. J Arthroplasty 2009;24(5):698. 15. Sendtner E, Borowiak K, Schuster T, et al. Tackling the learning curve: comparison between the anterior, minimally invasive (Micro-hip(R)) and the lateral, transgluteal (Bauer) approach for primary total hip replacement. Arch Orthop Trauma Surg 2011;131(5):597. 16. Lewinnek GE, Lewis JL, Tarr R, et al. Dislocations after total hip-replacement arthroplasties. J Bone Joint Surg Am 1978;60(2):217. 17. Shoukri MM, Pause CA. Statistical methods for health sciences. Boca Raton, FL: CRC Press; 1998. 18. Shrout PE, Fleiss JL. Intraclass correlations: uses in assessing rater reliability. Psychol Bull 1979;86(2):420. 19. Bender B, Nogler M, Hozack WJ. Direct anterior approach for total hip arthroplasty. Orthop Clin North Am 2009;40(3):321. 20. Moore AT. The self-locking metal hip prosthesis. J Bone Joint Surg Am 1957;39A(4):811.
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