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Range of motion of large head total hip arthroplasty is greater than 28 mm total hip arthroplasty or hip resurfacing
Clinical Biomechanics 26 (2011) 267–273
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Clinical Biomechanics j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / c l i n b i o m e c h
Range of motion of large head total hip arthroplasty is greater than 28 mm total hip arthroplasty or hip resurfacing☆ Martin Lavigne b,⁎, Muthu Ganapathi c, Sophie Mottard a, Julien Girard a, Pascal-André Vendittoli b a b c
Maisonneuve-Rosemont Hospital, Montreal, Quebec, Canada Department of Surgery, Montreal University, Quebec, Canada Department of Orthopaedics, Ysbyty Gwynedd, Bangor, United Kingdom
a r t i c l e
i n f o
Article history: Received 15 April 2010 Accepted 1 November 2010 Keywords: Range of motion Large diameter head total hip arthropalsty Hip resurfacing Function
a b s t r a c t Background: Reduced range of motion of the hip has a detrimental influence on lower limb function. Large diameter head total hip arthroplasty may theoretically have a greater potential for restoring normal hip range of motion due to greater head–neck diameter ratio, and hence provide better function compared to conventional or hip resurfacing arthroplasty. Method: At minimum one year follow-up, range of motion of the operated and contra lateral hips was clinically assessed using digital photographs and bony landmarks in a clinical comparative study. We assessed if 1) large diameter head total hip arthroplasty (55 patients) restores better hip range of motion compared to 28 mm total hip arthroplasty (50 patients) or hip resurfacing (60 patients) 2) large diameter head total hip arthroplasty achieves same hip range of motion as contra lateral normal hips and 3) hip range of motion correlates with the WOMAC score. Findings: The large diameter head total hip arthroplasty group had significantly greater total arcs of motion (approximately 20°), mostly due to an increase of hip flexion and external rotation, but did not reach normal hip motion. The hip range of motion showed significant correlation with the WOMAC score, especially the flexion arc. Interpretation: The better hip range of motion of large diameter head total hip arthroplasty is likely due to the greater head to neck diameter ratio and hence seems to be the best option to optimize range of hip motion and improve function after hip arthroplasty. © 2010 Elsevier Ltd. All rights reserved.
1. Introduction Pain and decreased range of motion (RoM) are the two most frequent symptoms of osteo arthritis of the hip (OA) and therefore, pain relief and restoration of mobility remain the primary objectives of total hip arthroplasty (THA). Although the relationship between RoM and satisfaction or better functional outcome has been clearly demonstrated after total knee arthroplasty (Park et al., 2007; Ritter and Campbell, 1987; Rossi et al., 2006; Weeden and Schmidt, 2007), the relationship between RoM of the hip joint and clinical outcome after hip arthroplasty has not been given as much interest. Nevertheless, reduced hip RoM has been shown to increase lower limb disability (Escalante et al., 1999; Odding et al., 1996; Steultjens
☆ Each author certifies that his or her institution has approved the human protocol for this investigation, that all investigations were conducted in conformity with ethical principles of research, and that informed consent for participation in the study was obtained. ⁎ Corresponding author. Hôpital Maisonneuve-Rosemont, 5345 Boul L'Assomption, Suite 55 Montréal, Québec, H1T 4B3, Canada. E-mail address: [email protected] (M. Lavigne). 0268-0033/$ – see front matter © 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.clinbiomech.2010.11.001
et al., 2000). A relationship also exists between restricted hip RoM and the Western Ontario MacMaster Osteoarthritis (WOMAC) Index (Davis et al., 2007; McGrory et al., 1996) or the patients' self assessment of the functional outcome (Bryant et al., 1993). Therefore, in order to further improve functional outcome after THA, restoration of natural hip motion would seem desirable. The influence of different prosthetic parameters and implant positions on RoM of the hip after THA has been studied extensively, but mainly in vitro with mathematical models (Widmer and Majewski, 2005), computer models (D'Lima et al., 2000; Kessler et al., 2008, Kluess et al., 2008), cadaveric specimens (Amstutz et al., 1975; Chandler et al., 1982; Gondi et al., 1997; Matsushita et al., 2009) or saw bone experiments (Bengs et al., 2008; Burroughs et al., 2005; Williams et al., 2009). To our knowledge only two clinical studies were devoted to comparing hip RoM obtained after two types of hip arthroplasty procedures (Le Duff et al., 2009; Vail et al., 2006). LeDuff compared RoM of the hip (method of measurement not described) in 35 patients with hip resurfacing (HR) on one side and stemmed type THA on the other side. The side of the stemmed type THA comprised 40% of revision cases and the size of the femoral heads varied from 28 mm to 50 mm. They found no difference in RoM between HR and
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stemmed type THA. Conversely Vail et al. demonstrated a significantly greater hip RoM score after HR compared to 28 or 32 mm THA. However, the measurements were made by multiple non blinded examiners and, as in LeDuff's study, the groups of patients were not homogenous. Although it remains to be clinically proven, one theoretical advantage of using larger diameter femoral heads in hip arthroplasty is increased RoM because of the greater head to neck diameter ratio (Burroughs et al., 2005; D'Lima et al., 2000, Kessler et al., 2008; Matsushita et al., 2009). If this theoretical advantage truly translates into increased clinical hip RoM, large diameter head total hip arthroplasty (LDH-THA) may provide the patient with a more functional hip joint. The primary goal of this study was to assess whether LDH-THA provides greater clinical RoM compared to 28 mm THA or HR at minimum one year post operatively. Secondary objectives included: 1) comparison of hip RoM of LDH-THA to normal contra lateral hips and 2) the correlation between hip RoM and the WOMAC functional score. 2. Methods This is a cohort study including patients less than 65 year old who received one of three types of arthroplasty (large diameter head THA, conventional 28 mm THA or hybrid HR). All patients with more than one year follow-up were asked to participate to this study when presenting to the hospital outpatient clinic between February 2006 and May 2007 for their routine follow-up evaluation. Patients were not enrolled in the study if they did not wish to participate, if they had or were planned to have a reoperation on their hip joint or if they complained of pain on passive RoM of the hip joint during routine physical examination. Assessment of hip RoM was performed only on the side with the longest follow-up in patients with bilateral hip arthroplasty (n = 26). We enrolled 55 patients in the LDH-THA group, 50 patients in the 28 mm THA group and 60 patients in the HR group. Among the patients included in the study, we identified all patients with a contra lateral asymptomatic, normal hip joint showing no radiological signs of osteoarthritis, Hip RoM was measured on the normal non-operated side of each of those patients, irrespective of the type of arthroplasty they had received on the diseased side (n = 86). Average RoM was calculated for each arc of hip motion to obtain comparative normal values. This study received approval from the scientific and ethics committees of our institution. All procedures were performed in the lateral decubitus position through a posterior surgical approach by three hip surgeons who had considerable experience with the three procedures. Circumferential capsulotomy was performed routinely in HR and selectively in 28 mm THA and LDH-THA groups at the surgeon's discretion when extending the hip past neutral was difficult. The implants used in the 28 mm THA group included a CLS femoral stem with a 12/14 Morse taper, a 28 mm Metasul femoral head in all patients, a Metasul poly sandwich metal liner and an Allofit acetabular cup (Zimmer, Warsaw, IN, USA). In the LDH-THA group, a CLS femoral stem, a Durom femoral head (size ranging from 38 mm to 58 mm with an average size of 46.6 mm) with a neck adapter and a Durom acetabular component (Zimmer, Warsaw, IN, USA) were used. The hip joint biomechanics (leg length, femoral offset, and hip center of rotation) was restored according to the contra lateral hip joint. The target for acetabular component position was 45° of abduction and 20° of anteversion in all cases. Anteversion of the femoral stem was aimed at 10°. For HR, we used the cemented Durom femoral and uncemented acetabular components (Zimmer, Warsaw, IN, USA). The Durom femoral component wall is 4 mm thick and the estimated cement mantle is 1 mm, giving an offset of 5 mm in relation to the opening of the component. The choice of femoral component size depended on a balance between restoration of head neck diameter ratio and acetabular bone conservation (Vendittoli et al., 2006, 2007). In this study, HR femoral
component sizes ranged from 40 mm to 58 mm with an average of 46.6 mm. An effort was made to restore normal offset of the anterior femoral neck by removing anterior neck osteophytes, translating the femoral component anteriorly or performing a careful neck osteoplasty when necessary. No acetabular component was found to be retroverted as assessed on cross table lateral views of the hip joint (Woo and Morrey, 1982). The post operative physical therapy protocol included progressive full weight bearing from the first post operative day and the same strengthening and stretching exercises in all groups. No flexion past 90° and no combined adduction–internal rotation were allowed in the 28 mm THA group for 6 weeks post operatively, whereas only flexion was limited to 90° for 2–4 weeks in HR and LDH-THA to allow healing of capsule and short rotators, without other RoM restrictions. The primary outcome measure of this study consisted of the following. At minimum one year after surgery, hip RoM measurements were performed by one examiner blinded with regards to the side and type of surgery with a technique developed to maximize reliability and precision of the measurements. Each individual arc of motion (flexion, extension, abduction, adduction, internal and external rotations) were measured and a total arc of hip RoM was calculated by adding each individual motion. The arc of rotation was measured in three positions: with the patient lying supine, in ventral decubitus (prone position) or lying supine with legs hanging at the end of the table. Therefore, we report three different total arcs of hip motion. A Western Ontario McMaster Osteoarthritic Index (WOMAC score) (Bellamy et al., 1988) was completed preoperatively and at last follow-up, and the occurrence of dislocation was recorded. The WOMAC score (scale from 0 to 100, the lowest score of 0 reflecting the best functional outcome) includes 24 questions related to 3 domains of hip function (pain, motion and physical activity). 2.1. Sample size calculation and statistical analysis The sample size was calculated according to our primary hypothesis: The clinical RoM of the hip joint should be greater after LDH-THA compared to 28 mm THA or HR. According to Klassbo et al. (2003) the standard deviation (SD) of the mean total arc of motion in normal or arthritic hip joints is 28 and 30.8, respectively. Therefore we estimated a SD of the mean total arc of motion of 30 to be conservative. We considered that a difference of at least 20° in the total arc of motion of the hip joint would be clinically significant. This would help a patient changing from the average motion group to the high motion group as defined by Davis et al. (2007) and would therefore facilitate the performance of some activities of daily living (Davis et al., 2007; Johnston and Smidt, 1970; Mulholland and Wyss, 2001). The significance level was set at 0.05. With a power of 80%, 144 patients (48 per group) were necessary to demonstrate a statistical difference in RoM between LDH-THA, 28 mm THA and HR. To assess the presence of significant differences between the 3 study groups, continuous demographic data and categorical demographic data were analyzed with one-way analysis of variance (ANOVA) and Chi-squared test respectively. For our primary outcome assessing whether greater hip RoM was observed in LDH-THA compared to 28 mm THA and HR, one-way ANOVA was first conducted to verify if there was a significant difference between the 3 types of prosthesis with regard to each individual and total arcs of hip RoM. The independent variable was the prosthesis type (HR, 28 mm THA and LDH-THA) while the dependent variables were the different arcs of motions. For some arcs of motion (total arc in prone, supine and leg hanging positions), the assumption of homogeneity of variances was not respected and therefore post hoc comparisons using the Tamhane's T2 test were conducted. Homogeneity of variances in arcs of motion was confirmed in all other arcs of motion and therefore we conducted post hoc comparisons using the Tukey test. For the second question of this study, the average arcs of hip RoM
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Fig. 1. Photograph showing marking of bony land marks.
of LDH-THA were compared to the average arcs of motion calculated on the normal side of pooled patients with unilateral hip involvement with the T-test for equality of means. Finally, for the last question of this study, all patients were pooled into one group and Spearman correlation coefficients were calculated to evaluate the relationship between the different arcs of hip RoM and the WOMAC score. P value equal or less than 0.05 was considered statistically significant. Method of RoM assessment (please refer to supplementary file for further details): Osseous landmarks including both anterior superior iliac spines (ASIS), tip of greater trochanters, lateral epicondyles of knees, center of patellae, tibial tubercles, and midpoint of the ankle joints were palpated and identified with a marking pen (Fig. 1). Digital photographs of the patient were taken in the resting neutral position and after reaching passive maximal motion in each arc of hip motion as defined by pelvic motion or soft tissue resistance. All photographs were taken at a fixed distance of 4 ft from the patient. Photographs were all centered on the hip joint, pubic symphysis or tibia depending on the arc of motion assessed (Figs. 2–4). The assessor could not look at the patient's buttock to avoid identifying the surgical scar. The assistant taking the photographs was responsible for uncovering the greater trochanter skin marks during flexion and extension assessments. The arcs of motion were calculated with Mesurim software (http://www.acamiens.fr/svt/outilprat/Mesurim/Index.htm) on the digital photographs by another evaluator who was also blinded to the type and side of surgery. On each digital photograph, the evaluator had to define the line joining the osseous landmarks or the table plane to allow the computer to calculate the corresponding angle. 3. Results No difference between the three study groups was found for gender (HR 68% male, 28 mm THA 62% male, LDH-THA 58% male, P value = 0.52), diagnosis of OA (HR 79%, 28 mm THA 74%, LDH-THA 70%, P value = 0.58), age (HR mean 48.9 years, range 25–64 and SD = 9.1; 28 mm THA mean 52.3 years, range 36–65 and SD = 7.4; LDH-THA mean 48.8 years, range 27–65 and SD 9.5, P value = 0.08) and pre operative WOMAC score (HR mean 49.5, range 24–75 and SD = 15.7; 28 mm THA mean 53.1, range 31–80 and SD = 17.4; LDHTHA mean 52.7, range 29–81 and SD 18.5, P value = 0.29). The Body Mass Index (BMI) of the 28 mm THA group (mean 28.7, range 21.1– 39.5 and SD 4.3) was significantly different from HR (mean 26.5, range 17.6–40 and SD 4.7, P = 0.025) and LDH-THA (mean 26.2, range 19.3– 39.6 and SD 4.3, P = 0.037) groups. The average follow-up was shorter in the LDH-THA group (mean 16.4 months, range 13–24 and SD 3.1) compared to 28 mm THA (mean 20.3 months, range 14–37 and SD 4.4,
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P = 0.048) and HR (20.1 months, range 12–40 and SD 5.1, P = 0.042). The WOMAC scores obtained at last follow-up were not statistically significant between the groups (HR mean 5.5, range 0–24 and SD = 15.2; 28 mm THA mean 7.1, range 0–30 and SD = 14.4; LDHTHA mean 5.9, range 0–20 and SD 10.4, P value = 0.82). Pre operative hip RoM was routinely assessed in all patients scheduled for hip arthroplasty as part of the baseline clinical data collection by a research assistant. Preoperative RoM assessment was performed in all HR and 28 mm THA patients, and in 48 of the 55 LDH-THA patients, the remaining 7 patients having incomplete data. There was no significant difference for all the preoperative arcs of hip RoM between the LDHTHA (total arc = 160°, SD 33.1), 28 mm THA groups (total arc = 161°, SD 38.1) and HR (total arc = 171°, SD 46.3) (P value = 0.26). The LDH-THA group showed significantly greater total arcs of hip motion (sum of all individual arcs) compared to the 28 mm THA and HR groups, except for a similar total arc in supine position vs. HR (P = 0.136). Furthermore, significant differences in hip RoM were found when LDH-THA was compared to both 28 mm THA and HR for all individual arcs of hip RoM (see Table 1 for P values), except for the abduction–adduction arc (P = 0.174) and arc of rotation in supine position (P = 0.152). The improvements of hip RoM of LDH-THA in the flexion–extension arc was due to better flexion (LDH-THA mean flexion 112.4, range 87.6–133.4 and SD 10.4; 28 mm THA mean flexion 102.8, range 74.4–132.9 and SD 10.2; HR mean flexion 103, range 69.8–124.6 and SD 11.8; P b 0.001) and for the arcs of rotation, to greater external rotation (ER) (values described here are for prone position: LDH-THA mean ER 36.7, range 18–51.3 and SD 7.4; 28 mm THA mean ER 27.5, range 8.9–49.3 and SD 11.7; HR mean ER 28.1, range 12.8–53.2 and SD 9.8; P = 0.003). The statistical power of the comparisons of the post operative total arcs of hip motion between the three study groups was 66%, 81% and 94% with the rotations taken in supine, prone and legs hanging positions, respectively. Pre operatively, the hip flexion was less than 90° in 17 LDH-THA, 22 patients with 28 mm THA and 19 HR (P = 0.491). Post operatively, the hip flexion was less than 90° in 7/60 (11.7%) HR, 4/50 (8%) THA and only 2/55 (3.6%) LDH-THA, but this was not statistically significant (P = 0.279). No difference was found between HR and 28 mm THA for all individual and total arcs of hip motion (P N 0.05). The total arcs of motion were significantly greater on the asymptomatic non-operated side of pooled patients with unilateral OA (total arc prone: mean 265.9° and SD 23.8, P = 0.006, Total arc legs hanging: mean 256.1° and SD 26.2, P = 0.027, total arc supine 259.1° and SD 23, P = 0.009) compared to the corresponding arcs in the LDHTHA group (see Table 1). The correlation coefficients between the WOMAC score and the individual arcs of hip motion measured in the 165 patients of the study were statistically significant, with hip flexion showing the strongest association (r = −0.329, P = 0.009). The correlation coefficients for the total arc of hip motion were as follows: Total arc in ventral decubitus: r = − 0.213, P = 0.013, Total arc with legs hanging: r = − 0.202, P = 0.024, Total arc in dorsal decubitus: r = −0.196, P = 0.042. Among the components of the WOMAC score, difficulty to put socks on showed the highest correlation with hip flexion (r = −0.279, P = 0.007). One dislocation occurred in 28 mm THA and none in LDH-THA and HR groups. The dislocation occurred only once at 4 days postoperatively, and was reduced under sedation. This patient was not excluded from the study. 4. Discussion Restoring optimal RoM after hip arthroplasty is critical for the patient's outcome as mobility is intimately related to certain functional capacity. For example, Davis et al. (2007) found that hip motion correlated with postoperative hip function such as using stairs and putting on socks and shoes. (Bryant et al., 1993) has shown that hip motion correlated with stair climbing ability, the
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Table 1 Comparisons of the different post operative arcs of hip motion measured in the three study groups. Arc of motion (mean, SD)
Study group HR
Flexion–Extension Flexion only Abduction–Adduction Rotation in prone External rotation (prone) only Rotation with legs hanging Rotation in supine Total arc (rotation in prone) Total arc (rotation with legs hanging) Total arc (rotation in supine)
117.4 103 55.9 51.5 28.1 47.6 51.0 224.9 220.9 224.6
(16.1) (11.8) (17.5) (16.9) (9.8) (15.5) (15.8) (43.4) (40.7) (42.1)
28 mm THA
LDH-THA
116.6 102.8 52.1 50.8 27.5 45.2 51.1 218.9 214.5 220.0
124.6 112.4 57.9 64.1 36.7 55.0 56.3 246.6 237.5 238.8
(12.6) (10.2) (12.4) (16.4) (11.5) (15.0) (15.4) (31.6) (30.2) (31.9)
(11.6) (10.4) (15.8) (11.9) (7.4) (11.8) (15.6) (27.5) (29.6) (32.0)
P value (Anova)
P value post hoc test HR vs. LDH-THA
THA vs. LDH-THA
0.007 b0.001 0.174 b0.001 0.003 0.003 0.152 b0.001 0.004 0.031
0.018 b0.001 0.897 b0.001 0.018 0.022 0.183 0.006 0.042 0.136
0.013 b 0.001 0.137 b 0.001 0.004 0.003 0.232 b 0.001 0.001 0.015
HR = hip resurfacing, 28 mm THA = conventional total hip arthroplasty with a 28 mm diameter femoral head, LDH-THA = large diameter head total hip arthroplasty, SD = standard deviation.
ease of tying shoes and the patients' perception of their own function. Restricted flexion of the hips was the strongest determinant of locomotor disability as determined by using six questions of a health assessment questionnaire (Odding et al., 1996). Therefore, with the aim of optimizing the functional outcome after hip arthroplasty, it would seem desirable to maximize the RoM of the reconstructed hip joint. The beneficial influence of using a larger head diameter with a small prosthetic neck diameter on the impingement-free hip RoM has been extensively studied, but almost exclusively in vitro (Amstutz et al., 1975; Bengs et al., 2008, Chandler et al., 1982; Clarke, 1982, D'Lima et al., 2000; Gondi et al., 1997; Kessler et al., 2008; Widmer and Majewski, 2005; Williams et al., 2009). In this study using a standardized method for assessing hip motion with blinded evaluators, we asked whether the favorable head to neck diameter ratio of the LDH-THA would permit detection of greater hip RoM compared to 28 mm THA and HR at more than one year post surgery. The patients enrolled in this study were not randomized. We agree that a randomized study would provide the best study design to test our primary hypothesis. However, we believe the three study groups to be comparable. The clinical scores and demographic data (WOMAC score, age, gender, and diagnosis) were similar, except for a slightly greater BMI in the 28 mm THA group. The pre operative RoM of all groups, which is an important factor influencing post operative hip
RoM, was similar (dela Rosa et al., 2007; Woolson et al., 1985). The average follow-up was shorter by 4 months in the LDH-THA group, but despite this potentially being unfavorable with regards to the recovery of hip RoM (Woolson et al., 1985), the measured hip RoM was still greater in LDH-THA, confirming the superiority of this implant to restore better hip motion. Although precise assessment of RoM of the hip and other joints is an extremely difficult task (Lea and Gerhardt, 1995), we believe the results of this study to be valid. The same observer who was blinded with regards to the type and side of surgery performed the RoM assessments for all three types of implants, in homogenous groups of patients and in several different patient positions with a standardized method that was proven to be reproducible. Blinding the observer is especially important to avoid limiting maximum hip RoM in 28 mm THA by fear of dislocation. The maximum motion was recorded when pelvic motion was visualized. This could have underestimated the functional hip RoM in LDH-THA and HR since the subluxation phase (from impingement to dislocation) with large heads results in greater degrees of motion (Matsushita et al., 2009). It must be noted that the value obtained for each arc of motion with our measurement method may not represent the true RoM. However, since the same method of measurement was done in all patients, we believe the differences in arc of motion we have reported are valid. Finally the RoM assessments were done passively with no contribution from the lumbosacral
Fig. 2. Photograph showing measurement of abduction.
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Fig. 3. Photographs showing measurement of flexion.
region, which does not represent the true functional dynamic combinations of movements occurring in real life. We have found only one clinical study reporting hip RoM after LDHTHA (Le Duff et al., 2009). Le Duff compared hip RoM after HR and total hip arthroplasty, some with femoral head diameters greater than 40 mm. Contrary to our results, he could not demonstrate differences in hip RoM between both groups. However, only 13 patients in the total hip arthroplasty group had femoral heads greater than 40 mm. Moreover, 40% of patients in the THA group were revision surgeries. Our study has shown statistically greater post operative hip RoM after LDH-THA compared to HR and 28 mm THA. As per our primary hypothesis, the head to neck diameter ratio is likely to be the most important factor explaining the greater RoM of LDH-THA. Indeed, the head to neck diameter ratio of a normal hip varies from 1.2 to 1.5, whereas it may be as high as 4.0 with a 50 mm femoral head mounted on a prosthetic femoral neck with reduced geometry (Clarke, 1982).
The total arcs of hip motion in LDH-THA were increased by approximately 20° compared to HR and 28 mm THA. This was the threshold set for defining a clinically relevant difference in hip RoM, but we expected somewhat greater hip RoM in LDH-THA as in vitro studies have demonstrated improvement ranging from 10 to 20° only in the arc of flexion between 22 mm heads and larger heads up to 44 mm (Chandler et al., 1982; Kessler et al., 2008; Matsushita et al., 2009). A factor limiting the improvement of hip RoM in LDH-THA is the presence of extra articular impingement (greater trochanter on ischial tuberosity in extension and/or external rotation and greater trochanter on ilium or pubis with flexion and/or internal rotation) which occurs with femoral head diameter greater than 38 mm (Burroughs et al., 2005; Chandler et al., 1982; Kessler et al., 2008). Thus, bony impingement, along with soft tissue restraints, probably explains the similar arc of abduction–adduction and arc of rotation with the hip at 90° observed in all groups of this study. As for 28 mm
Fig. 4. Photograph showing measurement of external rotation in prone position.
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THA, restriction of post operative hip motion by the patient may have decreased the potential for RoM improvement. As for HR the greater dissection, and thus scarring, may have limited the potential gain in hip motion. Moreover, the reduction of femoral offset usually seen after HR (Girard et al., 2006), the impossibility of changing the femoral anteversion (Vendittoli et al., 2007) and the larger femoral neck (Kluess et al., 2008; Williams et al., 2009) may have reduced hip RoM. There have been two reports showing no difference in clinical hip RoM between HR and conventional THA (Le Duff et al., 2009; Vail et al., 2006), and this finding was also confirmed in our study. The total arcs of hip motion obtained after LDH-THA still lacked approximately 20° compared to contra lateral normal hip joint, whereas a deficit of approximately 40° persists in the total arcs of hip motion after 28 mm THA and HR. Hip RoM may continue to improve with time after hip arthroplasty due to tissue stretching, especially in patients with the more stable LDH-THA and HR systems. In the case hip RoM was to improve with time, impingement or the feeling of subluxation may limit the ultimate RoM achieved in the 28 mm THA group. Moreover, as opposed to LDH-THA, improvement in hip RoM with 28 mm THA may be harmful since a significant positive correlation between hip RoM and linear polyethylene wear and failure of locking acetabular cup mechanism was shown by Imai (Imai et al., 2009). As for HR, increased hip RoM with time may lead to painful impingement (Lavigne et al., 2008) or neck notching (Bengs et al., 2008). The impact of hip RoM on activities of daily living was confirmed in this study which showed a correlation between hip RoM and the WOMAC score, especially in the flexion arc. We believe that the observed 20° of increase in hip RoM of LDH-THA is clinically relevant, especially since contributed mainly from better hip flexion and external rotation. Davis et al. (2007) has observed that hip flexion and external rotation correlated the highest with functional outcome as measured by the WOMAC score. McGrory et al. (1996) also found that the WOMAC physical function score correlated significantly with hip flexion. Thus, LDH-THA can be especially helpful for patients adopting extremes of hip RoM due to job requirements or socio cultural habits, and may facilitate the performance of activity of daily living. LDH-THA may also be better suited to fulfill the high expectations of the young and active patient. As stiff hips usually remain stiff after hip arthroplasty (dela Rosa et al., 2007; Woolson et al., 1985), LDH-THA may also represent a better option in patients with stiffer pre operative hip joint since only 2 patients with LDH-THA showed hip flexion less than 90° post operatively. In conclusion, our study has shown that the LDH-THA offers better hip RoM compared to 28 mm THA and HR, and this is most likely due to a combination of a favorable prosthetic head neck diameter ratio and optimal hip stability. This conclusion is in accordance with in vitro studies, but it had never been demonstrated previously in clinical studies. The optimal RoM needed after hip arthroplasty differs from patients to patients as it depends on cultural habits, the type of sport or leisure activity and type of work. Nevertheless, LDH-THA seems better suited to fulfill the clinical needs of the patients. However, LDH-THA requires use of hard on hard metal bearing and the long term results and survivorship of these new implants should match that of conventional hip replacements before being considered to be the most optimal means of restoring near normal function following hip arthroplasty. Supplementary materials related to this article can be found online at doi:10.1016/j.clinbiomech.2010.11.001. References Amstutz, H.C., Lodwig, R.M., Schurman, D.J., Hodgson, A.G., 1975. Range of motion studies for total hip replacements. A comparative study with a new experimental apparatus. Clin Orthop Relat Res 124–130. Bellamy, N., Buchanan, W.W., Goldsmith, C.H., Campbell, J., Stitt, L.W., 1988. Validation study of WOMAC: a health status instrument for measuring clinically important patient relevant outcomes to antirheumatic drug therapy in patients with osteoarthritis of the hip or knee. J Rheumatol 15, 1833–1840.
Bengs, B.C., Sangiorgio, S.N., Ebramzadeh, E., 2008. Less range of motion with resurfacing arthroplasty than with total hip arthroplasty: in vitro examination of 8 designs. Acta Orthop 79, 755–762. Bryant, M.J., Kernohan, W.G., Nixon, J.R., Mollan, R.A., 1993. A statistical analysis of hip scores. J Bone Joint Surg Br 75, 705–709. Burroughs, B.R., Hallstrom, B., Golladay, G.J., Hoeffel, D., Harris, W.H., 2005. Range of motion and stability in total hip arthroplasty with 28-, 32-, 38-, and 44-mm femoral head sizes. J Arthroplasty 20, 11–19. Chandler, D.R., Glousman, R., Hull, D., Mcguire, P.J., Kim, I.S., Clarke, I.C., Sarmiento, A., 1982. Prosthetic hip range of motion and impingement. The effects of head and neck geometry. Clin Orthop Relat Res 284–291. Clarke, I.C., 1982. Symposium on surface replacement arthroplasty of the hip. Biomechanics: mutifactorial design choices—an essential compromise? Orthop Clin North Am 13, 681–707. Davis, K.E., Ritter, M.A., Berend, M.E., Meding, J.B., 2007. The importance of range of motion after total hip arthroplasty. Clin Orthop Relat Res 465, 180–184. Dela Rosa, M.A., Silva, M., Heisel, C., Reich, M., Schmalzried, T.P., 2007. Range of motion after total hip resurfacing. Orthopedics 30, 352–357. D'lima, D.D., Urquhart, A.G., Buehler, K.O., Walker, R.H., Colwell JR., C.W., 2000. The effect of the orientation of the acetabular and femoral components on the range of motion of the hip at different head–neck ratios. J Bone Joint Surg Am 82, 315–321. Escalante, A., Lichtenstein, M.J., Dhanda, R., Cornell, J.E., Hazuda, H.P., 1999. Determinants of hip and knee flexion range: results from the San Antonio Longitudinal Study of Aging. Arthritis Care Res 12, 8–18. Girard, J., Lavigne, M., Vendittoli, P.A., Roy, A.G., 2006. Biomechanical reconstruction of the hip: a randomised study comparing total hip resurfacing and total hip arthroplasty. J Bone Joint Surg Br 88, 721–726. Gondi, G., Roberson, J.R., Ganey, T.M., Shahriari, A., Hutton, W.C., 1997. Impingement after total hip arthroplasty related to prosthetic component selection and range of motion. J South Orthop Assoc 6, 266–272. Imai, H., Mashima, N., Takahashi, T., Yamamoto, H., 2009. The relationship between increased hip range of motion, wear, and locking mechanism failure in the harrisgalante acetabular component. J Arthroplasty 24, 892–897. Johnston, R.C., Smidt, G.L., 1970. Hip motion measurements for selected activities of daily living. Clin Orthop Relat Res 72, 205–215. Kessler, O., Patil, S., Wirth, S., Mayr, E., Colwell JR., C.W., D'lima, D.D., 2008. Bony impingement affects range of motion after total hip arthroplasty: a subject-specific approach. J Orthop Res 26, 443–452. Klassbo, M., Harms-Ringdahl, K., Larsson, G., 2003. Examination of passive RoM and capsular patterns in the hip. Physiother Res Int 8, 1–12. Kluess, D., Zietz, C., Lindner, T., Mittelmeier, W., Schmitz, K.P., Bader, R., 2008. Limited range of motion of hip resurfacing arthroplasty due to unfavorable ratio of prosthetic head size and femoral neck diameter. Acta Orthop 79, 748–754. Lavigne, M., Boddu Siva Rama, K.R., Roy, A., Vendittoli, P.A., 2008. Painful impingement of the hip joint after total hip resurfacing: a report of two cases. J Arthroplasty 23, 1074–1079. Le Duff, M.J., Wisk, L.E., Amstutz, H.C., 2009. Range of motion after stemmed total hip arthroplasty and hip resurfacing — a clinical study. Bull NYU Hosp Jt Dis 67, 177–181. Lea, R.D., Gerhardt, J.J., 1995. Range-of-motion measurements. J Bone Joint Surg Am 77, 784–798. Matsushita, A., Nakashima, Y., Jingushi, S., Yamamoto, T., Kuraoka, A., Iwamoto, Y., 2009. Effects of the femoral offset and the head size on the safe range of motion in total hip arthroplasty. J Arthroplasty 24, 646–651. Mcgrory, B.J., Freiberg, A.A., Shinar, A.A., Harris, W.H., 1996. Correlation of measured range of hip motion following total hip arthroplasty and responses to a questionnaire. J Arthroplasty 11, 565–571. Mulholland, S.J., Wyss, U.P., 2001. Activities of daily living in non-Western cultures: range of motion requirements for hip and knee joint implants. Int J Rehabil Res 24, 191–198. Odding, E., Valkenburg, H.A., Algra, D., Vandenouweland, F.A., Grobbee, D.E., Hofman, A., 1996. The association of abnormalities on physical examination of the hip and knee with locomotor disability in the Rotterdam Study. Br J Rheumatol 35, 884–890. Park, K.K., Chang, C.B., Kang, Y.G., Seong, S.C., Kim, T.K., 2007. Correlation of maximum flexion with clinical outcome after total knee replacement in Asian patients. J Bone Joint Surg Br 89, 604–608. Ritter, M.A., Campbell, E.D., 1987. Effect of range of motion on the success of a total knee arthroplasty. J Arthroplasty 2, 95–97. Rossi, M.D., Hasson, S., Kohia, M., Pineda, E., Bryan, W., 2006. Mobility and perceived function after total knee arthroplasty. J Arthroplasty 21, 6–12. Steultjens, M.P., Dekker, J., Van Baar, M.E., Oostendorp, R.A., BIJLSMA, J.W., 2000. Range of joint motion and disability in patients with osteoarthritis of the knee or hip. Rheumatology (Oxford) 39, 955–961. Vail, T.P., Mina, C.A., Yergler, J.D., Pietrobon, R., 2006. Metal-on-metal hip resurfacing compares favorably with THA at 2 years followup. Clin Orthop Relat Res 453, 123–131. Vendittoli, P.A., Lavigne, M., Girard, J., Roy, A.G., 2006. A randomised study comparing resection of acetabular bone at resurfacing and total hip replacement. J Bone Joint Surg Br 88, 997–1002. Vendittoli, P.A., Ganapathi, M., Nuno, N., Plamondon, D., Lavigne, M., 2007. Factors affecting hip range of motion in surface replacement arthroplasty. Clin Biomech 22, 1004–1012. Weeden, S.H., Schmidt, R., 2007. A randomized, prospective study of primary total knee components designed for increased flexion. 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Contents lists available at ScienceDirect
Clinical Biomechanics j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / c l i n b i o m e c h
Range of motion of large head total hip arthroplasty is greater than 28 mm total hip arthroplasty or hip resurfacing☆ Martin Lavigne b,⁎, Muthu Ganapathi c, Sophie Mottard a, Julien Girard a, Pascal-André Vendittoli b a b c
Maisonneuve-Rosemont Hospital, Montreal, Quebec, Canada Department of Surgery, Montreal University, Quebec, Canada Department of Orthopaedics, Ysbyty Gwynedd, Bangor, United Kingdom
a r t i c l e
i n f o
Article history: Received 15 April 2010 Accepted 1 November 2010 Keywords: Range of motion Large diameter head total hip arthropalsty Hip resurfacing Function
a b s t r a c t Background: Reduced range of motion of the hip has a detrimental influence on lower limb function. Large diameter head total hip arthroplasty may theoretically have a greater potential for restoring normal hip range of motion due to greater head–neck diameter ratio, and hence provide better function compared to conventional or hip resurfacing arthroplasty. Method: At minimum one year follow-up, range of motion of the operated and contra lateral hips was clinically assessed using digital photographs and bony landmarks in a clinical comparative study. We assessed if 1) large diameter head total hip arthroplasty (55 patients) restores better hip range of motion compared to 28 mm total hip arthroplasty (50 patients) or hip resurfacing (60 patients) 2) large diameter head total hip arthroplasty achieves same hip range of motion as contra lateral normal hips and 3) hip range of motion correlates with the WOMAC score. Findings: The large diameter head total hip arthroplasty group had significantly greater total arcs of motion (approximately 20°), mostly due to an increase of hip flexion and external rotation, but did not reach normal hip motion. The hip range of motion showed significant correlation with the WOMAC score, especially the flexion arc. Interpretation: The better hip range of motion of large diameter head total hip arthroplasty is likely due to the greater head to neck diameter ratio and hence seems to be the best option to optimize range of hip motion and improve function after hip arthroplasty. © 2010 Elsevier Ltd. All rights reserved.
1. Introduction Pain and decreased range of motion (RoM) are the two most frequent symptoms of osteo arthritis of the hip (OA) and therefore, pain relief and restoration of mobility remain the primary objectives of total hip arthroplasty (THA). Although the relationship between RoM and satisfaction or better functional outcome has been clearly demonstrated after total knee arthroplasty (Park et al., 2007; Ritter and Campbell, 1987; Rossi et al., 2006; Weeden and Schmidt, 2007), the relationship between RoM of the hip joint and clinical outcome after hip arthroplasty has not been given as much interest. Nevertheless, reduced hip RoM has been shown to increase lower limb disability (Escalante et al., 1999; Odding et al., 1996; Steultjens
☆ Each author certifies that his or her institution has approved the human protocol for this investigation, that all investigations were conducted in conformity with ethical principles of research, and that informed consent for participation in the study was obtained. ⁎ Corresponding author. Hôpital Maisonneuve-Rosemont, 5345 Boul L'Assomption, Suite 55 Montréal, Québec, H1T 4B3, Canada. E-mail address: [email protected] (M. Lavigne). 0268-0033/$ – see front matter © 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.clinbiomech.2010.11.001
et al., 2000). A relationship also exists between restricted hip RoM and the Western Ontario MacMaster Osteoarthritis (WOMAC) Index (Davis et al., 2007; McGrory et al., 1996) or the patients' self assessment of the functional outcome (Bryant et al., 1993). Therefore, in order to further improve functional outcome after THA, restoration of natural hip motion would seem desirable. The influence of different prosthetic parameters and implant positions on RoM of the hip after THA has been studied extensively, but mainly in vitro with mathematical models (Widmer and Majewski, 2005), computer models (D'Lima et al., 2000; Kessler et al., 2008, Kluess et al., 2008), cadaveric specimens (Amstutz et al., 1975; Chandler et al., 1982; Gondi et al., 1997; Matsushita et al., 2009) or saw bone experiments (Bengs et al., 2008; Burroughs et al., 2005; Williams et al., 2009). To our knowledge only two clinical studies were devoted to comparing hip RoM obtained after two types of hip arthroplasty procedures (Le Duff et al., 2009; Vail et al., 2006). LeDuff compared RoM of the hip (method of measurement not described) in 35 patients with hip resurfacing (HR) on one side and stemmed type THA on the other side. The side of the stemmed type THA comprised 40% of revision cases and the size of the femoral heads varied from 28 mm to 50 mm. They found no difference in RoM between HR and
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stemmed type THA. Conversely Vail et al. demonstrated a significantly greater hip RoM score after HR compared to 28 or 32 mm THA. However, the measurements were made by multiple non blinded examiners and, as in LeDuff's study, the groups of patients were not homogenous. Although it remains to be clinically proven, one theoretical advantage of using larger diameter femoral heads in hip arthroplasty is increased RoM because of the greater head to neck diameter ratio (Burroughs et al., 2005; D'Lima et al., 2000, Kessler et al., 2008; Matsushita et al., 2009). If this theoretical advantage truly translates into increased clinical hip RoM, large diameter head total hip arthroplasty (LDH-THA) may provide the patient with a more functional hip joint. The primary goal of this study was to assess whether LDH-THA provides greater clinical RoM compared to 28 mm THA or HR at minimum one year post operatively. Secondary objectives included: 1) comparison of hip RoM of LDH-THA to normal contra lateral hips and 2) the correlation between hip RoM and the WOMAC functional score. 2. Methods This is a cohort study including patients less than 65 year old who received one of three types of arthroplasty (large diameter head THA, conventional 28 mm THA or hybrid HR). All patients with more than one year follow-up were asked to participate to this study when presenting to the hospital outpatient clinic between February 2006 and May 2007 for their routine follow-up evaluation. Patients were not enrolled in the study if they did not wish to participate, if they had or were planned to have a reoperation on their hip joint or if they complained of pain on passive RoM of the hip joint during routine physical examination. Assessment of hip RoM was performed only on the side with the longest follow-up in patients with bilateral hip arthroplasty (n = 26). We enrolled 55 patients in the LDH-THA group, 50 patients in the 28 mm THA group and 60 patients in the HR group. Among the patients included in the study, we identified all patients with a contra lateral asymptomatic, normal hip joint showing no radiological signs of osteoarthritis, Hip RoM was measured on the normal non-operated side of each of those patients, irrespective of the type of arthroplasty they had received on the diseased side (n = 86). Average RoM was calculated for each arc of hip motion to obtain comparative normal values. This study received approval from the scientific and ethics committees of our institution. All procedures were performed in the lateral decubitus position through a posterior surgical approach by three hip surgeons who had considerable experience with the three procedures. Circumferential capsulotomy was performed routinely in HR and selectively in 28 mm THA and LDH-THA groups at the surgeon's discretion when extending the hip past neutral was difficult. The implants used in the 28 mm THA group included a CLS femoral stem with a 12/14 Morse taper, a 28 mm Metasul femoral head in all patients, a Metasul poly sandwich metal liner and an Allofit acetabular cup (Zimmer, Warsaw, IN, USA). In the LDH-THA group, a CLS femoral stem, a Durom femoral head (size ranging from 38 mm to 58 mm with an average size of 46.6 mm) with a neck adapter and a Durom acetabular component (Zimmer, Warsaw, IN, USA) were used. The hip joint biomechanics (leg length, femoral offset, and hip center of rotation) was restored according to the contra lateral hip joint. The target for acetabular component position was 45° of abduction and 20° of anteversion in all cases. Anteversion of the femoral stem was aimed at 10°. For HR, we used the cemented Durom femoral and uncemented acetabular components (Zimmer, Warsaw, IN, USA). The Durom femoral component wall is 4 mm thick and the estimated cement mantle is 1 mm, giving an offset of 5 mm in relation to the opening of the component. The choice of femoral component size depended on a balance between restoration of head neck diameter ratio and acetabular bone conservation (Vendittoli et al., 2006, 2007). In this study, HR femoral
component sizes ranged from 40 mm to 58 mm with an average of 46.6 mm. An effort was made to restore normal offset of the anterior femoral neck by removing anterior neck osteophytes, translating the femoral component anteriorly or performing a careful neck osteoplasty when necessary. No acetabular component was found to be retroverted as assessed on cross table lateral views of the hip joint (Woo and Morrey, 1982). The post operative physical therapy protocol included progressive full weight bearing from the first post operative day and the same strengthening and stretching exercises in all groups. No flexion past 90° and no combined adduction–internal rotation were allowed in the 28 mm THA group for 6 weeks post operatively, whereas only flexion was limited to 90° for 2–4 weeks in HR and LDH-THA to allow healing of capsule and short rotators, without other RoM restrictions. The primary outcome measure of this study consisted of the following. At minimum one year after surgery, hip RoM measurements were performed by one examiner blinded with regards to the side and type of surgery with a technique developed to maximize reliability and precision of the measurements. Each individual arc of motion (flexion, extension, abduction, adduction, internal and external rotations) were measured and a total arc of hip RoM was calculated by adding each individual motion. The arc of rotation was measured in three positions: with the patient lying supine, in ventral decubitus (prone position) or lying supine with legs hanging at the end of the table. Therefore, we report three different total arcs of hip motion. A Western Ontario McMaster Osteoarthritic Index (WOMAC score) (Bellamy et al., 1988) was completed preoperatively and at last follow-up, and the occurrence of dislocation was recorded. The WOMAC score (scale from 0 to 100, the lowest score of 0 reflecting the best functional outcome) includes 24 questions related to 3 domains of hip function (pain, motion and physical activity). 2.1. Sample size calculation and statistical analysis The sample size was calculated according to our primary hypothesis: The clinical RoM of the hip joint should be greater after LDH-THA compared to 28 mm THA or HR. According to Klassbo et al. (2003) the standard deviation (SD) of the mean total arc of motion in normal or arthritic hip joints is 28 and 30.8, respectively. Therefore we estimated a SD of the mean total arc of motion of 30 to be conservative. We considered that a difference of at least 20° in the total arc of motion of the hip joint would be clinically significant. This would help a patient changing from the average motion group to the high motion group as defined by Davis et al. (2007) and would therefore facilitate the performance of some activities of daily living (Davis et al., 2007; Johnston and Smidt, 1970; Mulholland and Wyss, 2001). The significance level was set at 0.05. With a power of 80%, 144 patients (48 per group) were necessary to demonstrate a statistical difference in RoM between LDH-THA, 28 mm THA and HR. To assess the presence of significant differences between the 3 study groups, continuous demographic data and categorical demographic data were analyzed with one-way analysis of variance (ANOVA) and Chi-squared test respectively. For our primary outcome assessing whether greater hip RoM was observed in LDH-THA compared to 28 mm THA and HR, one-way ANOVA was first conducted to verify if there was a significant difference between the 3 types of prosthesis with regard to each individual and total arcs of hip RoM. The independent variable was the prosthesis type (HR, 28 mm THA and LDH-THA) while the dependent variables were the different arcs of motions. For some arcs of motion (total arc in prone, supine and leg hanging positions), the assumption of homogeneity of variances was not respected and therefore post hoc comparisons using the Tamhane's T2 test were conducted. Homogeneity of variances in arcs of motion was confirmed in all other arcs of motion and therefore we conducted post hoc comparisons using the Tukey test. For the second question of this study, the average arcs of hip RoM
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Fig. 1. Photograph showing marking of bony land marks.
of LDH-THA were compared to the average arcs of motion calculated on the normal side of pooled patients with unilateral hip involvement with the T-test for equality of means. Finally, for the last question of this study, all patients were pooled into one group and Spearman correlation coefficients were calculated to evaluate the relationship between the different arcs of hip RoM and the WOMAC score. P value equal or less than 0.05 was considered statistically significant. Method of RoM assessment (please refer to supplementary file for further details): Osseous landmarks including both anterior superior iliac spines (ASIS), tip of greater trochanters, lateral epicondyles of knees, center of patellae, tibial tubercles, and midpoint of the ankle joints were palpated and identified with a marking pen (Fig. 1). Digital photographs of the patient were taken in the resting neutral position and after reaching passive maximal motion in each arc of hip motion as defined by pelvic motion or soft tissue resistance. All photographs were taken at a fixed distance of 4 ft from the patient. Photographs were all centered on the hip joint, pubic symphysis or tibia depending on the arc of motion assessed (Figs. 2–4). The assessor could not look at the patient's buttock to avoid identifying the surgical scar. The assistant taking the photographs was responsible for uncovering the greater trochanter skin marks during flexion and extension assessments. The arcs of motion were calculated with Mesurim software (http://www.acamiens.fr/svt/outilprat/Mesurim/Index.htm) on the digital photographs by another evaluator who was also blinded to the type and side of surgery. On each digital photograph, the evaluator had to define the line joining the osseous landmarks or the table plane to allow the computer to calculate the corresponding angle. 3. Results No difference between the three study groups was found for gender (HR 68% male, 28 mm THA 62% male, LDH-THA 58% male, P value = 0.52), diagnosis of OA (HR 79%, 28 mm THA 74%, LDH-THA 70%, P value = 0.58), age (HR mean 48.9 years, range 25–64 and SD = 9.1; 28 mm THA mean 52.3 years, range 36–65 and SD = 7.4; LDH-THA mean 48.8 years, range 27–65 and SD 9.5, P value = 0.08) and pre operative WOMAC score (HR mean 49.5, range 24–75 and SD = 15.7; 28 mm THA mean 53.1, range 31–80 and SD = 17.4; LDHTHA mean 52.7, range 29–81 and SD 18.5, P value = 0.29). The Body Mass Index (BMI) of the 28 mm THA group (mean 28.7, range 21.1– 39.5 and SD 4.3) was significantly different from HR (mean 26.5, range 17.6–40 and SD 4.7, P = 0.025) and LDH-THA (mean 26.2, range 19.3– 39.6 and SD 4.3, P = 0.037) groups. The average follow-up was shorter in the LDH-THA group (mean 16.4 months, range 13–24 and SD 3.1) compared to 28 mm THA (mean 20.3 months, range 14–37 and SD 4.4,
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P = 0.048) and HR (20.1 months, range 12–40 and SD 5.1, P = 0.042). The WOMAC scores obtained at last follow-up were not statistically significant between the groups (HR mean 5.5, range 0–24 and SD = 15.2; 28 mm THA mean 7.1, range 0–30 and SD = 14.4; LDHTHA mean 5.9, range 0–20 and SD 10.4, P value = 0.82). Pre operative hip RoM was routinely assessed in all patients scheduled for hip arthroplasty as part of the baseline clinical data collection by a research assistant. Preoperative RoM assessment was performed in all HR and 28 mm THA patients, and in 48 of the 55 LDH-THA patients, the remaining 7 patients having incomplete data. There was no significant difference for all the preoperative arcs of hip RoM between the LDHTHA (total arc = 160°, SD 33.1), 28 mm THA groups (total arc = 161°, SD 38.1) and HR (total arc = 171°, SD 46.3) (P value = 0.26). The LDH-THA group showed significantly greater total arcs of hip motion (sum of all individual arcs) compared to the 28 mm THA and HR groups, except for a similar total arc in supine position vs. HR (P = 0.136). Furthermore, significant differences in hip RoM were found when LDH-THA was compared to both 28 mm THA and HR for all individual arcs of hip RoM (see Table 1 for P values), except for the abduction–adduction arc (P = 0.174) and arc of rotation in supine position (P = 0.152). The improvements of hip RoM of LDH-THA in the flexion–extension arc was due to better flexion (LDH-THA mean flexion 112.4, range 87.6–133.4 and SD 10.4; 28 mm THA mean flexion 102.8, range 74.4–132.9 and SD 10.2; HR mean flexion 103, range 69.8–124.6 and SD 11.8; P b 0.001) and for the arcs of rotation, to greater external rotation (ER) (values described here are for prone position: LDH-THA mean ER 36.7, range 18–51.3 and SD 7.4; 28 mm THA mean ER 27.5, range 8.9–49.3 and SD 11.7; HR mean ER 28.1, range 12.8–53.2 and SD 9.8; P = 0.003). The statistical power of the comparisons of the post operative total arcs of hip motion between the three study groups was 66%, 81% and 94% with the rotations taken in supine, prone and legs hanging positions, respectively. Pre operatively, the hip flexion was less than 90° in 17 LDH-THA, 22 patients with 28 mm THA and 19 HR (P = 0.491). Post operatively, the hip flexion was less than 90° in 7/60 (11.7%) HR, 4/50 (8%) THA and only 2/55 (3.6%) LDH-THA, but this was not statistically significant (P = 0.279). No difference was found between HR and 28 mm THA for all individual and total arcs of hip motion (P N 0.05). The total arcs of motion were significantly greater on the asymptomatic non-operated side of pooled patients with unilateral OA (total arc prone: mean 265.9° and SD 23.8, P = 0.006, Total arc legs hanging: mean 256.1° and SD 26.2, P = 0.027, total arc supine 259.1° and SD 23, P = 0.009) compared to the corresponding arcs in the LDHTHA group (see Table 1). The correlation coefficients between the WOMAC score and the individual arcs of hip motion measured in the 165 patients of the study were statistically significant, with hip flexion showing the strongest association (r = −0.329, P = 0.009). The correlation coefficients for the total arc of hip motion were as follows: Total arc in ventral decubitus: r = − 0.213, P = 0.013, Total arc with legs hanging: r = − 0.202, P = 0.024, Total arc in dorsal decubitus: r = −0.196, P = 0.042. Among the components of the WOMAC score, difficulty to put socks on showed the highest correlation with hip flexion (r = −0.279, P = 0.007). One dislocation occurred in 28 mm THA and none in LDH-THA and HR groups. The dislocation occurred only once at 4 days postoperatively, and was reduced under sedation. This patient was not excluded from the study. 4. Discussion Restoring optimal RoM after hip arthroplasty is critical for the patient's outcome as mobility is intimately related to certain functional capacity. For example, Davis et al. (2007) found that hip motion correlated with postoperative hip function such as using stairs and putting on socks and shoes. (Bryant et al., 1993) has shown that hip motion correlated with stair climbing ability, the
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Table 1 Comparisons of the different post operative arcs of hip motion measured in the three study groups. Arc of motion (mean, SD)
Study group HR
Flexion–Extension Flexion only Abduction–Adduction Rotation in prone External rotation (prone) only Rotation with legs hanging Rotation in supine Total arc (rotation in prone) Total arc (rotation with legs hanging) Total arc (rotation in supine)
117.4 103 55.9 51.5 28.1 47.6 51.0 224.9 220.9 224.6
(16.1) (11.8) (17.5) (16.9) (9.8) (15.5) (15.8) (43.4) (40.7) (42.1)
28 mm THA
LDH-THA
116.6 102.8 52.1 50.8 27.5 45.2 51.1 218.9 214.5 220.0
124.6 112.4 57.9 64.1 36.7 55.0 56.3 246.6 237.5 238.8
(12.6) (10.2) (12.4) (16.4) (11.5) (15.0) (15.4) (31.6) (30.2) (31.9)
(11.6) (10.4) (15.8) (11.9) (7.4) (11.8) (15.6) (27.5) (29.6) (32.0)
P value (Anova)
P value post hoc test HR vs. LDH-THA
THA vs. LDH-THA
0.007 b0.001 0.174 b0.001 0.003 0.003 0.152 b0.001 0.004 0.031
0.018 b0.001 0.897 b0.001 0.018 0.022 0.183 0.006 0.042 0.136
0.013 b 0.001 0.137 b 0.001 0.004 0.003 0.232 b 0.001 0.001 0.015
HR = hip resurfacing, 28 mm THA = conventional total hip arthroplasty with a 28 mm diameter femoral head, LDH-THA = large diameter head total hip arthroplasty, SD = standard deviation.
ease of tying shoes and the patients' perception of their own function. Restricted flexion of the hips was the strongest determinant of locomotor disability as determined by using six questions of a health assessment questionnaire (Odding et al., 1996). Therefore, with the aim of optimizing the functional outcome after hip arthroplasty, it would seem desirable to maximize the RoM of the reconstructed hip joint. The beneficial influence of using a larger head diameter with a small prosthetic neck diameter on the impingement-free hip RoM has been extensively studied, but almost exclusively in vitro (Amstutz et al., 1975; Bengs et al., 2008, Chandler et al., 1982; Clarke, 1982, D'Lima et al., 2000; Gondi et al., 1997; Kessler et al., 2008; Widmer and Majewski, 2005; Williams et al., 2009). In this study using a standardized method for assessing hip motion with blinded evaluators, we asked whether the favorable head to neck diameter ratio of the LDH-THA would permit detection of greater hip RoM compared to 28 mm THA and HR at more than one year post surgery. The patients enrolled in this study were not randomized. We agree that a randomized study would provide the best study design to test our primary hypothesis. However, we believe the three study groups to be comparable. The clinical scores and demographic data (WOMAC score, age, gender, and diagnosis) were similar, except for a slightly greater BMI in the 28 mm THA group. The pre operative RoM of all groups, which is an important factor influencing post operative hip
RoM, was similar (dela Rosa et al., 2007; Woolson et al., 1985). The average follow-up was shorter by 4 months in the LDH-THA group, but despite this potentially being unfavorable with regards to the recovery of hip RoM (Woolson et al., 1985), the measured hip RoM was still greater in LDH-THA, confirming the superiority of this implant to restore better hip motion. Although precise assessment of RoM of the hip and other joints is an extremely difficult task (Lea and Gerhardt, 1995), we believe the results of this study to be valid. The same observer who was blinded with regards to the type and side of surgery performed the RoM assessments for all three types of implants, in homogenous groups of patients and in several different patient positions with a standardized method that was proven to be reproducible. Blinding the observer is especially important to avoid limiting maximum hip RoM in 28 mm THA by fear of dislocation. The maximum motion was recorded when pelvic motion was visualized. This could have underestimated the functional hip RoM in LDH-THA and HR since the subluxation phase (from impingement to dislocation) with large heads results in greater degrees of motion (Matsushita et al., 2009). It must be noted that the value obtained for each arc of motion with our measurement method may not represent the true RoM. However, since the same method of measurement was done in all patients, we believe the differences in arc of motion we have reported are valid. Finally the RoM assessments were done passively with no contribution from the lumbosacral
Fig. 2. Photograph showing measurement of abduction.
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Fig. 3. Photographs showing measurement of flexion.
region, which does not represent the true functional dynamic combinations of movements occurring in real life. We have found only one clinical study reporting hip RoM after LDHTHA (Le Duff et al., 2009). Le Duff compared hip RoM after HR and total hip arthroplasty, some with femoral head diameters greater than 40 mm. Contrary to our results, he could not demonstrate differences in hip RoM between both groups. However, only 13 patients in the total hip arthroplasty group had femoral heads greater than 40 mm. Moreover, 40% of patients in the THA group were revision surgeries. Our study has shown statistically greater post operative hip RoM after LDH-THA compared to HR and 28 mm THA. As per our primary hypothesis, the head to neck diameter ratio is likely to be the most important factor explaining the greater RoM of LDH-THA. Indeed, the head to neck diameter ratio of a normal hip varies from 1.2 to 1.5, whereas it may be as high as 4.0 with a 50 mm femoral head mounted on a prosthetic femoral neck with reduced geometry (Clarke, 1982).
The total arcs of hip motion in LDH-THA were increased by approximately 20° compared to HR and 28 mm THA. This was the threshold set for defining a clinically relevant difference in hip RoM, but we expected somewhat greater hip RoM in LDH-THA as in vitro studies have demonstrated improvement ranging from 10 to 20° only in the arc of flexion between 22 mm heads and larger heads up to 44 mm (Chandler et al., 1982; Kessler et al., 2008; Matsushita et al., 2009). A factor limiting the improvement of hip RoM in LDH-THA is the presence of extra articular impingement (greater trochanter on ischial tuberosity in extension and/or external rotation and greater trochanter on ilium or pubis with flexion and/or internal rotation) which occurs with femoral head diameter greater than 38 mm (Burroughs et al., 2005; Chandler et al., 1982; Kessler et al., 2008). Thus, bony impingement, along with soft tissue restraints, probably explains the similar arc of abduction–adduction and arc of rotation with the hip at 90° observed in all groups of this study. As for 28 mm
Fig. 4. Photograph showing measurement of external rotation in prone position.
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THA, restriction of post operative hip motion by the patient may have decreased the potential for RoM improvement. As for HR the greater dissection, and thus scarring, may have limited the potential gain in hip motion. Moreover, the reduction of femoral offset usually seen after HR (Girard et al., 2006), the impossibility of changing the femoral anteversion (Vendittoli et al., 2007) and the larger femoral neck (Kluess et al., 2008; Williams et al., 2009) may have reduced hip RoM. There have been two reports showing no difference in clinical hip RoM between HR and conventional THA (Le Duff et al., 2009; Vail et al., 2006), and this finding was also confirmed in our study. The total arcs of hip motion obtained after LDH-THA still lacked approximately 20° compared to contra lateral normal hip joint, whereas a deficit of approximately 40° persists in the total arcs of hip motion after 28 mm THA and HR. Hip RoM may continue to improve with time after hip arthroplasty due to tissue stretching, especially in patients with the more stable LDH-THA and HR systems. In the case hip RoM was to improve with time, impingement or the feeling of subluxation may limit the ultimate RoM achieved in the 28 mm THA group. Moreover, as opposed to LDH-THA, improvement in hip RoM with 28 mm THA may be harmful since a significant positive correlation between hip RoM and linear polyethylene wear and failure of locking acetabular cup mechanism was shown by Imai (Imai et al., 2009). As for HR, increased hip RoM with time may lead to painful impingement (Lavigne et al., 2008) or neck notching (Bengs et al., 2008). The impact of hip RoM on activities of daily living was confirmed in this study which showed a correlation between hip RoM and the WOMAC score, especially in the flexion arc. We believe that the observed 20° of increase in hip RoM of LDH-THA is clinically relevant, especially since contributed mainly from better hip flexion and external rotation. Davis et al. (2007) has observed that hip flexion and external rotation correlated the highest with functional outcome as measured by the WOMAC score. McGrory et al. (1996) also found that the WOMAC physical function score correlated significantly with hip flexion. Thus, LDH-THA can be especially helpful for patients adopting extremes of hip RoM due to job requirements or socio cultural habits, and may facilitate the performance of activity of daily living. LDH-THA may also be better suited to fulfill the high expectations of the young and active patient. As stiff hips usually remain stiff after hip arthroplasty (dela Rosa et al., 2007; Woolson et al., 1985), LDH-THA may also represent a better option in patients with stiffer pre operative hip joint since only 2 patients with LDH-THA showed hip flexion less than 90° post operatively. In conclusion, our study has shown that the LDH-THA offers better hip RoM compared to 28 mm THA and HR, and this is most likely due to a combination of a favorable prosthetic head neck diameter ratio and optimal hip stability. This conclusion is in accordance with in vitro studies, but it had never been demonstrated previously in clinical studies. The optimal RoM needed after hip arthroplasty differs from patients to patients as it depends on cultural habits, the type of sport or leisure activity and type of work. Nevertheless, LDH-THA seems better suited to fulfill the clinical needs of the patients. However, LDH-THA requires use of hard on hard metal bearing and the long term results and survivorship of these new implants should match that of conventional hip replacements before being considered to be the most optimal means of restoring near normal function following hip arthroplasty. Supplementary materials related to this article can be found online at doi:10.1016/j.clinbiomech.2010.11.001. References Amstutz, H.C., Lodwig, R.M., Schurman, D.J., Hodgson, A.G., 1975. Range of motion studies for total hip replacements. A comparative study with a new experimental apparatus. Clin Orthop Relat Res 124–130. Bellamy, N., Buchanan, W.W., Goldsmith, C.H., Campbell, J., Stitt, L.W., 1988. Validation study of WOMAC: a health status instrument for measuring clinically important patient relevant outcomes to antirheumatic drug therapy in patients with osteoarthritis of the hip or knee. J Rheumatol 15, 1833–1840.
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