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Increased Femoral Anteversion Influence Over Surgically Treated Recurrent Patellar Instability Patients
Increased Femoral Anteversion Influence Over Surgically Treated Recurrent Patellar Instability Patients Carlos Eduardo Franciozi, M.D., Ph.D., Luiz Felipe Ambra, M.D., Leonardo José Bernardes Albertoni, M.D., Pedro Debieux, M.D., Ph.D., Fernando Cury Rezende, M.D., Mauricio Ayres de Oliveira, M.D., Marcio de Castro Ferreira, M.D., and Marcus Vinícius Malheiros Luzo, M.D., Ph.D.
Purpose: To verify the influence that increased femoral anteversion (FA) has on patients with recurrent patellar instability (RPI) treated by anteromedialization tibial tubercle osteotomy (TTO) combined with medial patellofemoral ligament reconstruction (MPFLR) and to present the midterm outcomes of these patients. Methods: From January 2008 to August 2013, skeletally mature patients with RPI and tibial tubercle (TT)etrochlear groove (TG) 17 mm who underwent anteromedialization TTO combined with MPFLR were evaluated for J sign, patellar glide, apprehension test, increased FA, Caton index, trochlea dysplasia, TT-TG, Kujala, International Knee Documentation Committee subjective knee evaluation form, and Tegner. Increased FA was determined clinically by a difference of more than 30 between hip internal and external rotation, 70 or more of hip internal rotation, and 30 or more of femoral neck anteversion. A subgroup analysis involving increased FA was made. Results: Forty-eight patients composed the study group. Mean follow-up was 41.5 11.05 months. The J-sign was present in 86% before surgery and none postoperatively (P < .001). All patients had a positive apprehension test or a patellar luxation at the patellar glide test rated as grade 4 before surgery. After surgery, the mean glide was 1.29 0.45 with no apprehension (P < .001). Increased FA was present in 18.7%. Caton index before surgery was 1.11 0.21 and 0.99 0.11 postoperatively (P ¼ .004). Trochlea dysplasia was present in all patients. TT-TG preoperatively was 20.77 2.12 mm and 11.33 1.24 mm postoperatively (P < .001). Functional scores improved preoperatively to postoperatively (P < .001) with Kujala and International Knee Documentation Committee means: 59.08 to 84.37; 52.6 to 85.5, respectively. Tegner preinjury score was 5.4 and postoperatively was 5.2 (P ¼ .01). Increased FA group had worse Kujala compared with the normal FA group and worse Kujala improvement: 77.7 and 85.89 (P ¼ .012), and 21.7 and 26.1, respectively (P < .001). Conclusions: Increased FA in patients with RPI had a negative effect on the outcome of anteromedialization TTO combined with MPFLR. Combined anteromedialization TTO and MPFLR had good functional midterm outcomes in treating patients with RPI and TT-TG 17 mm. Level of Evidence: Level III, comparative study.
T
he surgical treatment for recurrent patellar instability (RPI) normally aims to correct maltracking and to restore the medial soft-tissue restraint. Proximal realignment normally is addressed to recover the medial stability and comprises medial patellofemoral ligament reconstruction (MPFLR), among others. Distal
realignment is represented by tibial tubercle osteotomy (TTO). These procedures can be performed individually or combined.1-11 Despite the good results obtained with these surgeries, a significant number of patients appear to have pain and instability or to develop them as late
From the Department of Orthopaedics and Traumatology, Escola Paulista de Medicina, Federal University of São Paulo (C.E.F., L.F.A., L.J.B.A., P.D., F.C.R., M.V.M.L.), São Paulo, SP; Hospital Regional Público do Leste (M.A.d.O.), Paragominas, PA; and Hospital do Coração (M.d.C.F.), São Paulo, SP, Brazil. The authors report the following potential conflicts of interest or sources of funding: C.E.F., L.J.B.A., and M.d.C.F. received money as consultants for Smith & Nephew. M.V.M.L. received money as a consultant for DePuy Synthes. C.E.F., L.J.B.A., M.d.C.F., and M.V.M.L. received payment for the development of educational presentations.
Received June 24, 2016; accepted September 16, 2016. Address correspondence to Carlos Eduardo Franciozi, M.D., Ph.D., Rua Borges Lagoa, 783, 5th Floor, Vila Clementino, São Paulo 04038-032, Brazil. E-mail: [email protected] Ó 2016 by the Arthroscopy Association of North America 0749-8063/16585/$36.00 http://dx.doi.org/10.1016/j.arthro.2016.09.015
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symptoms and then degenerate to osteoarthritis.10,12 Some authors have attributed this to unrecognized or uncorrected torsional inferior limb malalignment, and they argue that rotational deformity should be corrected through derotative osteotomies.5,13-17 Increased femoral internal torsion, also referred to as increased femoral anteversion (FA), has been pointed out as an underestimated villain and recently has been attributed to the proximal, mid-, and distal portions of the femur instead of just the proximal neck.18,19 In the knee, increased FA results in abnormal lateral patellofemoral loads and the tendency for lateral subluxation of the patella.5,14,16,20-23 Although this rotational malalignment is addressed as a primary risk factor for patellar dislocation, there is a paucity of studies describing its influence on surgeries not involving torsional osteotomies. The effect of rotational malalignment on TTO combined with MPFLR surgical treatment for RPI currently is unknown. The purpose of this study was to verify the influence increased FA has on patients with RPI treated by anteromedialization TTO combined with MPFLR and to present mid-term outcomes for these patients. We hypothesized that increased FA would have a negative effect on patients with RPI treated by anteromedialization TTO combined with MPFLR.
Methods From January 2008 to August 2013, 54 consecutive skeletally mature patients with RPI were enrolled to participate in this study. Inclusion criteria for MPFL reconstruction combined with Fulkerson’s TTO were defined as 2 or more episodes of patellar dislocation, skeletal maturity, positive apprehension test, and a tibial tubercleetrochlear groove (TT-TG) distance of 17 mm or more.8,10,24 Patients were excluded in cases of an absence of patellofemoral cartilage lesions and of patellar lesions Outerbridge grade 3 or 4 involving the medial facet or the proximal region and medial facet. The exclusion criteria were based on some anteromedialization TTO contraindications. All patients were enrolled in this study before surgery. All included patients underwent MPFLR and anteromedialization TTO as described by Fulkerson et al.6 One patient was excluded because of the absence of patellofemoral cartilage lesions and underwent medial TTO directly. Two patients were excluded because of Outerbridge grade 4 patellar lesions involving just the medial facet or the proximal region. The patient with a grade 4 lesion on the medial facet underwent MPFLR only and not TTO. Four subjects were excluded because they were lost to follow-up. Forty-eight patients were eligible for the study. This clinical database was approved by the institutional review board (Federal University of São Paulo [UNIFESP], São Paulo Hospital, approval
number: 32205914.1.0000.5505), and all patients provided signed informed consent to participate. Historical data were collected for each patient. The physical examination variables comprised the presence or absence of the J sign, patellar glide (lateral patellar translation) at 30 of flexion graded as 1, 2, 3, and 4 according to quadrants of lateral translation,25 evaluation of the apprehension sign,26 and the presence or absence of increased FA. To be considered as part of the increased FA subgroup, the patient had to fulfill 3 criteria: have differences of more than 30 between passive hip internal and external rotation, favoring internal rotation measured at the prone position; have 70 or more of hip internal rotation determined by the Staheli method in prone position; and have 30 or more of femoral neck anteversion as determined by the Ruwe method with the patient in a prone position.14,27-32 Radiographs of the knee included preoperative and postoperative anteroposterior (AP) and lateral views at 30 flexion. The Caton index33 was used to evaluate the height of the patella. A Caton index score >1.2 was considered a high patella. Trochlea dysplasia was evaluated by the 4 grades trochlear dysplasia classification.34 All 4 grades or the absence of dysplasia were used. Also, patients with dysplasia were divided into low grade (A) or high grade (B, C, D) to improve observer agreement.35 All patients underwent computed tomography (CT), and an independent reader, a musculoskeletal radiologist, measured TT-TG.3 Patient-reported outcomes were measured with the Kujala,36 the International Knee Documentation Committee (IKDC) subjective knee evaluation form,37 and Tegner Activity Scale.38 Tegner values preoperatively were rated as the activity level at the time just before the index injury and not the current impaired level at the initial physician visit. Also, sports participation was evaluated similarly with the Tegner Activity Scale. Sports participation was considered positive if the patient was involved in recreational or competitive sports at least twice a week. Surgical Technique The procedure began with a routine arthroscopic examination via the anterolateral and anteromedial portals. Articular cartilage was evaluated carefully. Lesions were evaluated for localization and size, and they were graded according to Outerbridge classification. The osteotomy was performed similarly as described by Fulkerson et al.6 The medialization distance to normalize the TT-TG to 10 to 12 mm was estimated from the preoperative CT measurements in millimeters. Lesser amounts of medialization normally were accompanied by increased obliquity. If distalization was necessary (Caton index >1.2), it was estimated from the lateral radiograph to normalize the Caton index to 1, and the tibial tubercle was detached fully. Once
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satisfactory tracking was achieved, final tibial tuberosity fixation was made with two 4.5-mm bicortical AO screws of appropriate length and washers. The MPFLR was performed with a semitendinosus autograft placed anatomically at the patella at the transition between the proximal and middle one-third of the medial border and at the femur 1 cm distal to the adductor tubercle and 1 cm posterior to the medial epicondyle that was being tested for isometry. Patella fixation was made with a 5-mm titanium anchor (Twinfix; Smith & Nephew, Andover, MA). The graft was routed at the second layer of the medial compartment from the patella to the femur by a Kelly clamp. Satisfactory isometry consisted of less than 3 mm migration during flexion-extension tested after patellar graft fixation. Femoral fixation was made by a bioabsorbable interference screw (BIORCI-HA; Smith & Nephew) at 60 flexion with a Kelly clamp underneath the graft to avoid overconstraint of the patellofemoral joint. Nonabsorbable protection sutures were applied to the graft, securing it to soft tissues at the patella and femur insertion sites. Fluoroscopy was used to check the patella and femur insertion sites before anchor insertion and tunnel confection. Also, it was used to certify implants and tunnel positions. After the end of this procedure, patellar tracking, range of movement, and lateral displacement of the patella were tested. The final objective was to have a slight lateral glide of just one quadrant with a distinctive end point in extension rather than no lateral glide, which could lead to increased pain, worse rehabilitation, and limited range of movement. Postoperative Rehabilitation Patients were wrapped with compression dressing, fitted with a knee brace, elevated. Range of movement was encouraged on the first postoperative day with the brace removed. Range of motion was increased based on the patient’s tolerance. Early isometric quadriceps exercises were begun. Patients were kept toe-touch weight bearing with a brace and crutches for the first 6 weeks. They progressed to progressive weight bearing with a brace and crutches for up to 8 weeks. After 8 weeks, the brace and crutches restrictions were discontinued based on the patient’s progression. Rehabilitation continued, with care to instruct the patient in patellofemoral-friendly exercises. Return to sport was based on the patient, surgical procedure, and sport, with greater risk sports such as soccer requiring a longer rehabilitation period. Statistical Analysis Means, standard deviation, range, and frequencies were used to describe patient demographics. The c2 test was used to detect differences between groups. The
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Wilcoxon signed-rank test was used to compare changes within each group from the preoperative state to follow-up. Mann-Whitney U tests and the Student t test were used to compare mean scores between groups preoperatively and at the latest follow-up and to compare changes from the preoperative state to the follow-up visit (difference scores) according to the normality and homogeneity of variances, nonparametric and parametric, respectively. Statistical significance was set at P < .05. The statistics were performed with statistics software RStudio Version 0.99.484 (2009-2015, RStudio).
Results During the period of study, 48 patients with RPI who underwent Fulkerson osteotomy and MPFLR with a minimum of 2 years follow-up were evaluated. Table 1 gives the details of demographic characteristics of the subjects. A great number were female (75%), and the mean follow-up was 41.5 months (range 24-60 months). Before surgery, 86% of the patients presented the J sign. After surgery, no patient presented it (P < .001). All patients had a positive apprehension test or a patellar luxation at the patellar glide test rated as grade 4 before surgery. Five patients had patellar luxation without apprehension. After surgery, the mean glide rate was 1.29 0.45 (range 1-2), and no patient had apprehension or luxation (P < .001). No patient experienced recurrent or single patellar dislocations after surgery. Clinical evaluation identified increased FA in 18.7% of the patients. Caton index score before surgery was 1.11 0.21 (range 0.6-1.97). After surgery, it was 0.99 0.11 (range 0.6-1.15). Distalization was required in 41% of patients (Caton index >1.2), and all of them presented with a Caton index score within the normal range after surgery <1.2, mean 1.07 0.04 (range 1-1.12) (P ¼ .004). Cartilage lesions were present at the patella of all included patients. Trochlear lesions were present in just 18% of the patients. Nine patients underwent surgical treatment of patellar cartilage lesions Outerbridge 4. Five were treated with microfracture, and 4 were treated with osteochondral autologous transplantation. Trochear dysplasia was present in all evaluated patients. Data from 3 patients were unavailable because of the poor quality of their lateral knee radiographs. The average of TT-TG preoperatively was 20.77 2.12 mm (range 17-27). After the procedure, the mean was 11.33 1.24 mm (range 10-15), demonstrating statistically significant improvement (P < .001). The primary outcome was functional evaluation, for which there was a statistical difference pre- and postoperatively for Kujala and IKDC. The Tegner was worse
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postoperatively; however, the difference was not clinically significant (Table 2). A subgroup analysis regarding the increased FA was performed. The increased FA group presented with the worst Kujala scores postoperatively and also the worst improvement on Kujala compared with the normal FA group. This difference was statistically significant. IKDC postoperative results were worse in the increased FA group; however, the difference was not statistically significant. IKDC improvement was statistically better regarding the increased FA group. Variables that could interfere with this result did not show any difference between the groups. Table 3 gives details of the demographic information of both groups as well as the functional assessment of the subjects. Also of note, in patients with increased FA, a distinct appearance of the knee on AP radiographs was recognized (Fig 1). This distinctive appearance was present in 89% of the increased FA group and in none of the normal FA group. Two patients required manipulation under anesthesia. A nondisplaced patellar fracture occurred in 1 patient at 12 weeks after surgery after a direct trauma to the knee, and it was treated nonoperatively with complete healing. Four patients required tibial tubercle screws and washer removal because of anterior discomfort at the implant site. Eleven patients had the other knee operated on as well, at least 8 months after the index surgery, but the data regarding the other knee were not included to avoid confounders and minimum 2 years of surgery follow-up.
Discussion The most important findings of this study were the worst patient-reported Kujala outcome, and the worst Kujala improvement presented in the increased FA group compared with the normal FA group, presenting a 8.19 Kujala outcome difference and a 20% greater improvement favoring the normal FA group.39,40 This finding demonstrates the negative influence that increased FA poses to patients with RPI treated by anteromedialization TTO combined with MPFLR. This finding also is an important contribution to the understanding of patellar instability, and it confirms the concerns of torsional deformity inferred by some studies and treatment algorithms.3,5,13-16,21,27,41,42 Also, this study showed that the anteromedialization TTO combined with MPFLR presents good functional results and yields return to almost the same level of sport activity in patients with RPI and TT-TG 17 mm. The contribution of femoral and tibial abnormal torsion to anterior knee pain and patellofemoral instability has long been underestimated.5,16,17,43 Torsional deformity, including the femur and tibia, could be addressed as the main problem in 12% of all patients with patellar maltracking according to Dickschas
et al.,13 which is in contrast to our greater 18.7% incidence of increased FA. This difference may be related to the population studied. In our study, we only included patients with RPI, and the referred study involved patients with patellar instability and also patients with anterior knee pain without instability. Some authors already have emphasized the relationship between increased FA and patellar instability.15,34 Dejour et al.3 found increased FA in patients with objective patellar instability compared with controls, 15.6 and 10.8 , respectively, which is also inferior to our findings. Basically, the main population difference between this study and Dejour et al.3 was a greater TTTG; however, no correlation was found between TT-TG and increased FA. Diederichs et al.15 also found a 1.56fold greater mean FA in patients with patellofemoral instability compared with controls, emphasizing this important relationship. Throughout the gait, normally, the knee joint axis moves internally relative to the pelvis during the stance phase and externally during the swing phase. Increased FA leads to an abnormal internally rotated gait with the knee joint axis pointing medially while the body is moving forward. This leads to an even greater internal rotation of the knee joint axis during stance phase, causing excessive lateral pull on the patella. This excessive pull increases distraction on MPFL and loads on the lateral side of the patellofemoral joint while decreasing it on the medial side. Consequently, increased FA results in abnormal lateral patellofemoral pressure and the tendency for lateral subluxation.5,14,16,20-23 This increased hostile FA biomechanical environment for the patellofemoral joint can explain the inferior Kujala outcomes and improvement findings of this study. The addition of a derotational or torsional osteotomy may lead to better results for these patients. Because statistically significant research may not be clinically important, minimum clinically important difference was applied. Only the Kujala questionnaire showed clinically significant differences when we compared both FA groups. Interestingly, IKDC did not show any clinically significant differences regarding the FA groups. Because the minimum clinically important difference for IKDC is reported to be greater than the Kujala, 16.7 points compared with 8 to 10 points or 10%, respectively, even with a small difference, increased FA group Kujala scores and improvement were clinically and statistically significant whereas IKDC scores were not.39,40 Both questionnaires are well-established evaluation tools; however, the Kujala is more specific for the evaluation of patellofemoral disorder than IKDC. The IKDC is more generic, because it is used for a variety of knee conditions. There are some recently developed specific questionnaires for patellar instability, but they were not applied because they still require language validation. The Kujala was
FEMORAL ANTEVERSION AND PATELLAR INSTABILITY Table 1. Patient Information and Clinical Assessment
Table 3. Influence of FA
Measurements 48 25.22 6.6 36 (75)/12 (25) 9 (18.7) 41.5 11.05 20 (41.67) 1.34 0.52
Patients, n Age, yr, mean SD Sex, female/male (%) Increased FA, n (%) Follow-up, mo, mean SD Patella alta, n (%) Patella cartilage defect size, cm2, mean SD Grade I, n/% Grade II, n/% Grade III, n/% Grade IV, n/% Trochlear dysplasia (Dejour classification), n None Grade A Grade B Grade C Grade D Unavailable
5
5/10.4 16/33.3 17/35.42 10/20.83
0 17 17 7 4 3
FA, femoral anteversion; SD, standard deviation.
designed to document pain in the patellofemoral compartment and probably does not fully capture the subjective difficulties of patients with RPI; however, the Kujala questionnaire is still the most-used questionnaire for RPI.9,44 It is difficult to determine the exact values to define increased FA measured either by physical examination or by image examination. There is no consensus regarding the normal limits or the torsion threshold to indicate surgical correction by derotational osteotomy.18,19,21,27,28,30,31,42 Nevertheless, to successfully determine increased FA, some parameters were defined arbitrarily. The adopted criteria leave no question regarding the presence of this condition, even without the use of CT or magnetic resonance (MR) to confirm it. All 3 adopted criteria were well above the most commonly reported standard values. In addition, the patients had to fulfill all of them, and their reliability already has been proven in previous studies.21,27-32 Also, some of the values were based on
Increased FA Normal FA P Value Patients, n 9 39 Age, yr, mean SD 23.88 6.8 25.53 6.6 .5 Sex, female, n (%) 9 (100) 27 (69) .55 TT-TG, pre-, mean SD 21.33 1.65 20.64 2.21 .37 Patella alta, % 33 44 .42 Follow-up, mo, mean SD 36 8.4 42.76 11.28 .08 Defect size, mean SD 1.22 0.26 1.37 0.57 .74 Outerbridge 4 cartilage 2 (22.22) 8 (20.51) .11 defect, n (%) Trochlear dysplasia, n 9 36 .91 Grade A, % 39 33 Grade B, % 39 33 Grade C, % 14 22 Grade D, % 8 11 Trochlear dysplasia, n 9 36 .35 Low grade (A), % 39 33 High grade (B, C, D), % 61 67 Kujala Preoperatively 56 59.79 .15 Postoperatively 77.7 85.89 .012 Improvement 21.7 26.1 <.001 IKDC Preoperatively 46.21 54.11 .01 Postoperatively 81.43 86.44 .1 Improvement 35.22 32.33 .003 FA, femoral anteversion; IKDC, International Knee Documentation Committee; SD, standard deviation; TT-TG, tibial tubercleetrochlear groove.
Table 2. Function Measured Preoperatively and at Follow-up Measure Kujala Excellent (95) Good (85-94) Fair (65-84) Poor (65) IKDC Tegner SP, n (%) Tegner >5, n (%)
Preoperative 59.08 e e 25% 75% 52.6 5.4 16 (33) 13 (27)
Follow-up 84.37 6% 56% 31% 6% 85.5 5.2 13 (27) 12 (25)
Difference 25.29
32.87 0.15 3 (6) 1 (2)
P Value <.001
<.001 .01 e e
IKDC, International Knee Documentation Committee; SP, sports participation.
Fig 1. Inverted proximal humerus sign. (A) Patient with increased FA; AP radiograph of the right knee showing a bulbous and prominent lateral femoral condyle similar to a humerus head and a small and narrow medial femoral condyle similar to a humerus greater tuberosity; the whole image looks like a inverted proximal humerus. (B) Patient with normal FA; AP radiograph of the right knee showing the classical appearance of more symmetrical condyles with a distinguished medial condyle. (AP, anteroposterior; FA, femoral anteversion.)
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femoral derotation osteotomy from the surgical indications of previous studies.14,16,29,45 Although no CT or MR was used to determine FA, some of the arbitrarily determined values for increased FA also were decided on the basis of image-related research.13-16,18,19,21,41,45 Trochlear dysplasia can have a negative effect on the results of MPFLR used as treatment for RPI, as pointed out by some studies.46-48 Although some studies did not show this negative effect, FA subgroup analysis included the variables that could interfere in the results to eliminate confounders.7,49 Those, presented in Table 3, included trochlea dysplasia individually evaluated by each Dejour type (A, B, C, D) and grouped in low (type A) or high grades (type B, C, D) as previously suggested to improve observer agreement.35 All variables displayed a similar distribution in both groups of FA analysis, validating the statistically significant worst Kujala outcomes and improvement presented in the increased FA group. Also, a recent study demonstrated an important association between increased FA and trochlea dysplasia by the use of several parameters for trochlea morphology analysis and correlating them to the anteversion contribution of the proximal, diaphyseal, and distal portions of the femur.18 This relationship was not found in the present study, a result similar to others, probably because of an insufficiency of trochlear morphology parameters analyzed as proposed by Liebensteiner et al.15,18,50 In the patients with increased FA, a distinct appearance of the knee on the AP radiograph was recognized. The knee was similar to an upside-down proximal humerus with the lateral condyle representing the head and the medial condyle representing a greater tuberosity. Certainly an AP radiograph of the humerus is different, but its similarity was addressed by the authors as the “inverted proximal humerus sign.” This probably happens because the patients with increased FA have a tendency for lateral subluxation of the patella and for increased tilt resulting from internal torsion of the bone. Because the AP radiograph usually is performed with the patella pointing forward, the anterversionrotated appearance of the distal knee makes the lateral femoral condyle more bulbous and prominent and does the opposite to the medial condyle. This sign can be used as a possible indicator of increased FA and should alert surgeons to evaluate it more carefully in some patients. Possibly, the sign is more prominent as FA increases. See Figure 1. No patient reported functional failure (clinical apprehension sign, repeat subluxation, repeat dislocation, subjective instability) postoperatively in contrast to a mean 4.7% to 9.5% incidence at isolated MPFLR without TTO studies and 3% to 10% mean incidence at isolated TTO.10,11,24,51,52 This important difference may be related to the synergic protective function of an
associated MPFLR and TTO procedure. This association may be especially important in cases of severe trochlea dysplasia or important torsional malalignment that are not directly addressed by a trochleoplasty or torsional osteotomy, in addition to TT-TG distances >15 mm.5,8,9,11,51 Limitations The number of patients involved is not large, especially if considering only the subgroup with increased FA. Because of that and low power, there may be other undetected differences between the 2 groups we compared; however, the number is substantial regarding patients with RPI who underwent MPFLR and TTO and even more relevant if considering the small amount of studies involving anteromedialization TTO. Recruitment took 5 years to complete, and the sample size is similar to the majority of studies regarding the same topic.6,7,10,24,53 Nevertheless, the FA subgroup analysis showed statistically significant differences. No CT or MR was used to confirm increased FA, and no objective measurement data were analyzed with the intent to quantify the FA threshold at which derotation osteotomy should be considered. Instead, the FA subgroup analysis was divided in increased or normal FA. Notwithstanding, clinical examination has been used and validated to determine increased FA for a long time and is a reliable approach even today and in patients with cerebral palsy, who comprise much more complex torsional deformities, where the described methods are applied and used as surgical indication and guidance.27,29-32,54 In addition, 3 criteria that used 3 different methods were used to confirm the increased FA.27,30,31 Unfortunately, this study raises some questions but does not answer them regarding what the best surgical procedure is for patients with RPI and increased FA or how much increased FA is acceptable before a derotational osteotomy is indicated. This will be the focus of future studies with better methodology, ideally randomized clinical trials involving derotational osteotomies, MPFLR, and TTO. Nonetheless, the finding that increased FA can have a negative effect in patients with RPI treated with MPFLR and anteromedialization TTO is important to existing knowledge and dictates further investigation of this topic.
Conclusions Increased FA in patients with RPI had a negative effect on anteromedialization TTO combined with MPFLR. Combined anteromedialization TTO and MPFLR had good functional midterm outcomes in treating RPI patients with TT-TG 17 mm.
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syndrome: Surgical technique and clinical outcome. Int Orthop 2015;39:2355-2362. Paulos L, Swanson SC, Stoddard GJ, Barber-Westin S. Surgical correction of limb malalignment for instability of the patella: a comparison of 2 techniques. Am J Sports Med 2009;37:1288-1300. Liebensteiner MC, Ressler J, Seitlinger G, Djurdjevic T, El Attal R, Ferlic PW. High femoral anteversion is related to femoral trochlea dysplasia. Arthroscopy 2016;32: 2295-2299. Seitlinger G, Moroder P, Scheurecker G, Hofmann S, Grelsamer RP. The contribution of different femur segments to overall femoral torsion. Am J Sports Med 2016;44: 1796-1800. Lee TQ, Anzel SH, Bennett KA, Pang D, Kim WC. The influence of fixed rotational deformities of the femur on the patellofemoral contact pressures in human cadaver knees. Clin Orthop Relat Res 1994;(302):69-74. Teitge RA. Patellofemoral syndrome a paradigm for current surgical strategies. Orthop Clin North Am 2008;39: 287-311, v. Lee TQ, Morris G, Csintalan RP. The influence of tibial and femoral rotation on patellofemoral contact area and pressure. J Orthop Sports Phys Ther 2003;33:686-693. Besier TF, Gold GE, Delp SL, Fredericson M, Beaupre GS. The influence of femoral internal and external rotation on cartilage stresses within the patellofemoral joint. J Orthop Res 2008;26:1627-1635. Koeter S, Diks MJ, Anderson PG, Wymenga AB. A modified tibial tubercle osteotomy for patellar maltracking: Results at two years. J Bone Joint Surg Br 2007;89:180-185. Kolowich PA, Paulos LE, Rosenberg TD, Farnsworth S. Lateral release of the patella: Indications and contraindications. Am J Sports Med 1990;18:359-365. Fairbank HA. Internal derangement of the knee in children and adolescents: (Section of prthopaedics). Proc R Soc Med 1937;30:427-432. Cibulka MT. Determination and significance of femoral neck anteversion. Phys Ther 2004;84:550-558. Nakahara I, Takao M, Sakai T, Nishii T, Yoshikawa H, Sugano N. Gender differences in 3D morphology and bony impingement of human hips. J Orthop Res 2011;29: 333-339. Ounpuu S, DeLuca P, Davis R, Romness M. Long-term effects of femoral derotation osteotomies: An evaluation using three-dimensional gait analysis. J Pediatr Orthop 2002;22:139-145. Ruwe PA, Gage JR, Ozonoff MB, DeLuca PA. Clinical determination of femoral anteversion. A comparison with established techniques. J Bone Joint Surg Am 1992;74: 820-830. Staheli LT, Corbett M, Wyss C, King H. Lower-extremity rotational problems in children. Normal values to guide management. J Bone Joint Surg Am 1985;67:39-47. Skiak E, Karakasli A, Basci O, Satoglu IS, Ertem F, Havitcioglu H. Distal femoral derotational osteotomy with external fixation for correction of excessive femoral anteversion in patients with cerebral palsy. J Pediatr Orthop B 2015;24:425-432.
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33. Caton J. Method of measuring the height of the patella. Acta Orthop Belg 1989;55:385-386 [in French]. 34. Dejour D, Le Coultre B. Osteotomies in patello-femoral instabilities. Sports Med Arthrosc 2007;15:39-46. 35. Lippacher S, Dejour D, Elsharkawi M, et al. Observer agreement on the Dejour trochlear dysplasia classification: A comparison of true lateral radiographs and axial magnetic resonance images. Am J Sports Med 2012;40:837-843. 36. Kujala UM, Jaakkola LH, Koskinen SK, Taimela S, Hurme M, Nelimarkka O. Scoring of patellofemoral disorders. Arthroscopy 1993;9:159-163. 37. Hefti F, Muller W, Jakob RP, Staubli HU. Evaluation of knee ligament injuries with the IKDC form. Knee Surg Sports Traumatol Arthrosc 1993;1:226-234. 38. Tegner Y, Lysholm J. Rating systems in the evaluation of knee ligament injuries. Clin Orthop Relat Res 1985:43-49. 39. Crossley KM, Bennell KL, Cowan SM, Green S. Analysis of outcome measures for persons with patellofemoral pain: Which are reliable and valid? Arch Phys Med Rehabil 2004;85:815-822. 40. Greco NJ, Anderson AF, Mann BJ, et al. Responsiveness of the International Knee Documentation Committee Subjective Knee Form in comparison to the Western Ontario and McMaster Universities Osteoarthritis Index, modified Cincinnati Knee Rating System, and Short Form 36 in patients with focal articular cartilage defects. Am J Sports Med 2010;38:891-902. 41. Schueda MA, Astur DC, Bier RS, Bier DS, Astur N, Cohen M. Use of computed tomography to determine the risk of patellar dislocation in 921 patients with patellar instability. Open Access J Sports Med 2015;6:55-62. 42. Weber AE, Nathani A, Dines JS, et al. An algorithmic approach to the management of recurrent lateral patellar dislocation. J Bone Joint Surg Am 2016;98:417-427. 43. Cooke TD, Price N, Fisher B, Hedden D. The inwardly pointing knee. An unrecognized problem of external rotational malalignment. Clin Orthop Relat Res 1990;(260): 56-60. 44. Wang D, Jones MH, Khair MM, Miniaci A. Patient-reported outcome measures for the knee. J Knee Surg 2010;23:137-151.
45. Bruce WD, Stevens PM. Surgical correction of miserable malalignment syndrome. J Pediatr Orthop 2004;24:392-396. 46. Wagner D, Pfalzer F, Hingelbaum S, Huth J, Mauch F, Bauer G. The influence of risk factors on clinical outcomes following anatomical medial patellofemoral ligament (MPFL) reconstruction using the gracilis tendon. Knee Surg Sports Traumatol Arthrosc 2013;21:318-324. 47. Hiemstra LA, Kerslake S, Loewen M, Lafave M. Effect of trochlear dysplasia on outcomes after isolated soft tissue stabilization for patellar instability. Am J Sports Med 2016;44:1515-1523. 48. Kita K, Tanaka Y, Toritsuka Y, et al. Factors affecting the outcomes of double-bundle medial patellofemoral ligament reconstruction for recurrent patellar dislocations evaluated by multivariate analysis. Am J Sports Med 2015;43:2988-2996. 49. Steiner TM, Torga-Spak R, Teitge RA. Medial patellofemoral ligament reconstruction in patients with lateral patellar instability and trochlear dysplasia. Am J Sports Med 2006;34:1254-1261. 50. Wright SJ, Boymans TA, Grimm B, Miles AW, Kessler O. Strong correlation between the morphology of the proximal femur and the geometry of the distal femoral trochlea. Knee Surg Sports Traumatol Arthrosc 2014;22:2900-2910. 51. Stupay KL, Swart E, Shubin Stein BE. Widespread implementation of medial patellofemoral ligament reconstruction for recurrent patellar instability maintains functional outcomes at midterm to long-term follow-up while decreasing complication rates: A systematic review. Arthroscopy 2015;31:1372-1380. 52. Matic GT, Magnussen RA, Kolovich GP, Flanigan DC. Return to activity after medial patellofemoral ligament repair or reconstruction. Arthroscopy 2014;30:1018-1025. 53. Payne J, Rimmke N, Schmitt LC, Flanigan DC, Magnussen RA. The incidence of complications of tibial tubercle osteotomy: A systematic review. Arthroscopy 2015;31:1819-1825. 54. Swanson AB, Greene PW Jr, Allis HD. Rotational deformities of the lower extremity in children and their clinical significance. Clin Orthop Relat Res 1963;27: 157-175.
Purpose: To verify the influence that increased femoral anteversion (FA) has on patients with recurrent patellar instability (RPI) treated by anteromedialization tibial tubercle osteotomy (TTO) combined with medial patellofemoral ligament reconstruction (MPFLR) and to present the midterm outcomes of these patients. Methods: From January 2008 to August 2013, skeletally mature patients with RPI and tibial tubercle (TT)etrochlear groove (TG) 17 mm who underwent anteromedialization TTO combined with MPFLR were evaluated for J sign, patellar glide, apprehension test, increased FA, Caton index, trochlea dysplasia, TT-TG, Kujala, International Knee Documentation Committee subjective knee evaluation form, and Tegner. Increased FA was determined clinically by a difference of more than 30 between hip internal and external rotation, 70 or more of hip internal rotation, and 30 or more of femoral neck anteversion. A subgroup analysis involving increased FA was made. Results: Forty-eight patients composed the study group. Mean follow-up was 41.5 11.05 months. The J-sign was present in 86% before surgery and none postoperatively (P < .001). All patients had a positive apprehension test or a patellar luxation at the patellar glide test rated as grade 4 before surgery. After surgery, the mean glide was 1.29 0.45 with no apprehension (P < .001). Increased FA was present in 18.7%. Caton index before surgery was 1.11 0.21 and 0.99 0.11 postoperatively (P ¼ .004). Trochlea dysplasia was present in all patients. TT-TG preoperatively was 20.77 2.12 mm and 11.33 1.24 mm postoperatively (P < .001). Functional scores improved preoperatively to postoperatively (P < .001) with Kujala and International Knee Documentation Committee means: 59.08 to 84.37; 52.6 to 85.5, respectively. Tegner preinjury score was 5.4 and postoperatively was 5.2 (P ¼ .01). Increased FA group had worse Kujala compared with the normal FA group and worse Kujala improvement: 77.7 and 85.89 (P ¼ .012), and 21.7 and 26.1, respectively (P < .001). Conclusions: Increased FA in patients with RPI had a negative effect on the outcome of anteromedialization TTO combined with MPFLR. Combined anteromedialization TTO and MPFLR had good functional midterm outcomes in treating patients with RPI and TT-TG 17 mm. Level of Evidence: Level III, comparative study.
T
he surgical treatment for recurrent patellar instability (RPI) normally aims to correct maltracking and to restore the medial soft-tissue restraint. Proximal realignment normally is addressed to recover the medial stability and comprises medial patellofemoral ligament reconstruction (MPFLR), among others. Distal
realignment is represented by tibial tubercle osteotomy (TTO). These procedures can be performed individually or combined.1-11 Despite the good results obtained with these surgeries, a significant number of patients appear to have pain and instability or to develop them as late
From the Department of Orthopaedics and Traumatology, Escola Paulista de Medicina, Federal University of São Paulo (C.E.F., L.F.A., L.J.B.A., P.D., F.C.R., M.V.M.L.), São Paulo, SP; Hospital Regional Público do Leste (M.A.d.O.), Paragominas, PA; and Hospital do Coração (M.d.C.F.), São Paulo, SP, Brazil. The authors report the following potential conflicts of interest or sources of funding: C.E.F., L.J.B.A., and M.d.C.F. received money as consultants for Smith & Nephew. M.V.M.L. received money as a consultant for DePuy Synthes. C.E.F., L.J.B.A., M.d.C.F., and M.V.M.L. received payment for the development of educational presentations.
Received June 24, 2016; accepted September 16, 2016. Address correspondence to Carlos Eduardo Franciozi, M.D., Ph.D., Rua Borges Lagoa, 783, 5th Floor, Vila Clementino, São Paulo 04038-032, Brazil. E-mail: [email protected] Ó 2016 by the Arthroscopy Association of North America 0749-8063/16585/$36.00 http://dx.doi.org/10.1016/j.arthro.2016.09.015
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symptoms and then degenerate to osteoarthritis.10,12 Some authors have attributed this to unrecognized or uncorrected torsional inferior limb malalignment, and they argue that rotational deformity should be corrected through derotative osteotomies.5,13-17 Increased femoral internal torsion, also referred to as increased femoral anteversion (FA), has been pointed out as an underestimated villain and recently has been attributed to the proximal, mid-, and distal portions of the femur instead of just the proximal neck.18,19 In the knee, increased FA results in abnormal lateral patellofemoral loads and the tendency for lateral subluxation of the patella.5,14,16,20-23 Although this rotational malalignment is addressed as a primary risk factor for patellar dislocation, there is a paucity of studies describing its influence on surgeries not involving torsional osteotomies. The effect of rotational malalignment on TTO combined with MPFLR surgical treatment for RPI currently is unknown. The purpose of this study was to verify the influence increased FA has on patients with RPI treated by anteromedialization TTO combined with MPFLR and to present mid-term outcomes for these patients. We hypothesized that increased FA would have a negative effect on patients with RPI treated by anteromedialization TTO combined with MPFLR.
Methods From January 2008 to August 2013, 54 consecutive skeletally mature patients with RPI were enrolled to participate in this study. Inclusion criteria for MPFL reconstruction combined with Fulkerson’s TTO were defined as 2 or more episodes of patellar dislocation, skeletal maturity, positive apprehension test, and a tibial tubercleetrochlear groove (TT-TG) distance of 17 mm or more.8,10,24 Patients were excluded in cases of an absence of patellofemoral cartilage lesions and of patellar lesions Outerbridge grade 3 or 4 involving the medial facet or the proximal region and medial facet. The exclusion criteria were based on some anteromedialization TTO contraindications. All patients were enrolled in this study before surgery. All included patients underwent MPFLR and anteromedialization TTO as described by Fulkerson et al.6 One patient was excluded because of the absence of patellofemoral cartilage lesions and underwent medial TTO directly. Two patients were excluded because of Outerbridge grade 4 patellar lesions involving just the medial facet or the proximal region. The patient with a grade 4 lesion on the medial facet underwent MPFLR only and not TTO. Four subjects were excluded because they were lost to follow-up. Forty-eight patients were eligible for the study. This clinical database was approved by the institutional review board (Federal University of São Paulo [UNIFESP], São Paulo Hospital, approval
number: 32205914.1.0000.5505), and all patients provided signed informed consent to participate. Historical data were collected for each patient. The physical examination variables comprised the presence or absence of the J sign, patellar glide (lateral patellar translation) at 30 of flexion graded as 1, 2, 3, and 4 according to quadrants of lateral translation,25 evaluation of the apprehension sign,26 and the presence or absence of increased FA. To be considered as part of the increased FA subgroup, the patient had to fulfill 3 criteria: have differences of more than 30 between passive hip internal and external rotation, favoring internal rotation measured at the prone position; have 70 or more of hip internal rotation determined by the Staheli method in prone position; and have 30 or more of femoral neck anteversion as determined by the Ruwe method with the patient in a prone position.14,27-32 Radiographs of the knee included preoperative and postoperative anteroposterior (AP) and lateral views at 30 flexion. The Caton index33 was used to evaluate the height of the patella. A Caton index score >1.2 was considered a high patella. Trochlea dysplasia was evaluated by the 4 grades trochlear dysplasia classification.34 All 4 grades or the absence of dysplasia were used. Also, patients with dysplasia were divided into low grade (A) or high grade (B, C, D) to improve observer agreement.35 All patients underwent computed tomography (CT), and an independent reader, a musculoskeletal radiologist, measured TT-TG.3 Patient-reported outcomes were measured with the Kujala,36 the International Knee Documentation Committee (IKDC) subjective knee evaluation form,37 and Tegner Activity Scale.38 Tegner values preoperatively were rated as the activity level at the time just before the index injury and not the current impaired level at the initial physician visit. Also, sports participation was evaluated similarly with the Tegner Activity Scale. Sports participation was considered positive if the patient was involved in recreational or competitive sports at least twice a week. Surgical Technique The procedure began with a routine arthroscopic examination via the anterolateral and anteromedial portals. Articular cartilage was evaluated carefully. Lesions were evaluated for localization and size, and they were graded according to Outerbridge classification. The osteotomy was performed similarly as described by Fulkerson et al.6 The medialization distance to normalize the TT-TG to 10 to 12 mm was estimated from the preoperative CT measurements in millimeters. Lesser amounts of medialization normally were accompanied by increased obliquity. If distalization was necessary (Caton index >1.2), it was estimated from the lateral radiograph to normalize the Caton index to 1, and the tibial tubercle was detached fully. Once
FEMORAL ANTEVERSION AND PATELLAR INSTABILITY
satisfactory tracking was achieved, final tibial tuberosity fixation was made with two 4.5-mm bicortical AO screws of appropriate length and washers. The MPFLR was performed with a semitendinosus autograft placed anatomically at the patella at the transition between the proximal and middle one-third of the medial border and at the femur 1 cm distal to the adductor tubercle and 1 cm posterior to the medial epicondyle that was being tested for isometry. Patella fixation was made with a 5-mm titanium anchor (Twinfix; Smith & Nephew, Andover, MA). The graft was routed at the second layer of the medial compartment from the patella to the femur by a Kelly clamp. Satisfactory isometry consisted of less than 3 mm migration during flexion-extension tested after patellar graft fixation. Femoral fixation was made by a bioabsorbable interference screw (BIORCI-HA; Smith & Nephew) at 60 flexion with a Kelly clamp underneath the graft to avoid overconstraint of the patellofemoral joint. Nonabsorbable protection sutures were applied to the graft, securing it to soft tissues at the patella and femur insertion sites. Fluoroscopy was used to check the patella and femur insertion sites before anchor insertion and tunnel confection. Also, it was used to certify implants and tunnel positions. After the end of this procedure, patellar tracking, range of movement, and lateral displacement of the patella were tested. The final objective was to have a slight lateral glide of just one quadrant with a distinctive end point in extension rather than no lateral glide, which could lead to increased pain, worse rehabilitation, and limited range of movement. Postoperative Rehabilitation Patients were wrapped with compression dressing, fitted with a knee brace, elevated. Range of movement was encouraged on the first postoperative day with the brace removed. Range of motion was increased based on the patient’s tolerance. Early isometric quadriceps exercises were begun. Patients were kept toe-touch weight bearing with a brace and crutches for the first 6 weeks. They progressed to progressive weight bearing with a brace and crutches for up to 8 weeks. After 8 weeks, the brace and crutches restrictions were discontinued based on the patient’s progression. Rehabilitation continued, with care to instruct the patient in patellofemoral-friendly exercises. Return to sport was based on the patient, surgical procedure, and sport, with greater risk sports such as soccer requiring a longer rehabilitation period. Statistical Analysis Means, standard deviation, range, and frequencies were used to describe patient demographics. The c2 test was used to detect differences between groups. The
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Wilcoxon signed-rank test was used to compare changes within each group from the preoperative state to follow-up. Mann-Whitney U tests and the Student t test were used to compare mean scores between groups preoperatively and at the latest follow-up and to compare changes from the preoperative state to the follow-up visit (difference scores) according to the normality and homogeneity of variances, nonparametric and parametric, respectively. Statistical significance was set at P < .05. The statistics were performed with statistics software RStudio Version 0.99.484 (2009-2015, RStudio).
Results During the period of study, 48 patients with RPI who underwent Fulkerson osteotomy and MPFLR with a minimum of 2 years follow-up were evaluated. Table 1 gives the details of demographic characteristics of the subjects. A great number were female (75%), and the mean follow-up was 41.5 months (range 24-60 months). Before surgery, 86% of the patients presented the J sign. After surgery, no patient presented it (P < .001). All patients had a positive apprehension test or a patellar luxation at the patellar glide test rated as grade 4 before surgery. Five patients had patellar luxation without apprehension. After surgery, the mean glide rate was 1.29 0.45 (range 1-2), and no patient had apprehension or luxation (P < .001). No patient experienced recurrent or single patellar dislocations after surgery. Clinical evaluation identified increased FA in 18.7% of the patients. Caton index score before surgery was 1.11 0.21 (range 0.6-1.97). After surgery, it was 0.99 0.11 (range 0.6-1.15). Distalization was required in 41% of patients (Caton index >1.2), and all of them presented with a Caton index score within the normal range after surgery <1.2, mean 1.07 0.04 (range 1-1.12) (P ¼ .004). Cartilage lesions were present at the patella of all included patients. Trochlear lesions were present in just 18% of the patients. Nine patients underwent surgical treatment of patellar cartilage lesions Outerbridge 4. Five were treated with microfracture, and 4 were treated with osteochondral autologous transplantation. Trochear dysplasia was present in all evaluated patients. Data from 3 patients were unavailable because of the poor quality of their lateral knee radiographs. The average of TT-TG preoperatively was 20.77 2.12 mm (range 17-27). After the procedure, the mean was 11.33 1.24 mm (range 10-15), demonstrating statistically significant improvement (P < .001). The primary outcome was functional evaluation, for which there was a statistical difference pre- and postoperatively for Kujala and IKDC. The Tegner was worse
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postoperatively; however, the difference was not clinically significant (Table 2). A subgroup analysis regarding the increased FA was performed. The increased FA group presented with the worst Kujala scores postoperatively and also the worst improvement on Kujala compared with the normal FA group. This difference was statistically significant. IKDC postoperative results were worse in the increased FA group; however, the difference was not statistically significant. IKDC improvement was statistically better regarding the increased FA group. Variables that could interfere with this result did not show any difference between the groups. Table 3 gives details of the demographic information of both groups as well as the functional assessment of the subjects. Also of note, in patients with increased FA, a distinct appearance of the knee on AP radiographs was recognized (Fig 1). This distinctive appearance was present in 89% of the increased FA group and in none of the normal FA group. Two patients required manipulation under anesthesia. A nondisplaced patellar fracture occurred in 1 patient at 12 weeks after surgery after a direct trauma to the knee, and it was treated nonoperatively with complete healing. Four patients required tibial tubercle screws and washer removal because of anterior discomfort at the implant site. Eleven patients had the other knee operated on as well, at least 8 months after the index surgery, but the data regarding the other knee were not included to avoid confounders and minimum 2 years of surgery follow-up.
Discussion The most important findings of this study were the worst patient-reported Kujala outcome, and the worst Kujala improvement presented in the increased FA group compared with the normal FA group, presenting a 8.19 Kujala outcome difference and a 20% greater improvement favoring the normal FA group.39,40 This finding demonstrates the negative influence that increased FA poses to patients with RPI treated by anteromedialization TTO combined with MPFLR. This finding also is an important contribution to the understanding of patellar instability, and it confirms the concerns of torsional deformity inferred by some studies and treatment algorithms.3,5,13-16,21,27,41,42 Also, this study showed that the anteromedialization TTO combined with MPFLR presents good functional results and yields return to almost the same level of sport activity in patients with RPI and TT-TG 17 mm. The contribution of femoral and tibial abnormal torsion to anterior knee pain and patellofemoral instability has long been underestimated.5,16,17,43 Torsional deformity, including the femur and tibia, could be addressed as the main problem in 12% of all patients with patellar maltracking according to Dickschas
et al.,13 which is in contrast to our greater 18.7% incidence of increased FA. This difference may be related to the population studied. In our study, we only included patients with RPI, and the referred study involved patients with patellar instability and also patients with anterior knee pain without instability. Some authors already have emphasized the relationship between increased FA and patellar instability.15,34 Dejour et al.3 found increased FA in patients with objective patellar instability compared with controls, 15.6 and 10.8 , respectively, which is also inferior to our findings. Basically, the main population difference between this study and Dejour et al.3 was a greater TTTG; however, no correlation was found between TT-TG and increased FA. Diederichs et al.15 also found a 1.56fold greater mean FA in patients with patellofemoral instability compared with controls, emphasizing this important relationship. Throughout the gait, normally, the knee joint axis moves internally relative to the pelvis during the stance phase and externally during the swing phase. Increased FA leads to an abnormal internally rotated gait with the knee joint axis pointing medially while the body is moving forward. This leads to an even greater internal rotation of the knee joint axis during stance phase, causing excessive lateral pull on the patella. This excessive pull increases distraction on MPFL and loads on the lateral side of the patellofemoral joint while decreasing it on the medial side. Consequently, increased FA results in abnormal lateral patellofemoral pressure and the tendency for lateral subluxation.5,14,16,20-23 This increased hostile FA biomechanical environment for the patellofemoral joint can explain the inferior Kujala outcomes and improvement findings of this study. The addition of a derotational or torsional osteotomy may lead to better results for these patients. Because statistically significant research may not be clinically important, minimum clinically important difference was applied. Only the Kujala questionnaire showed clinically significant differences when we compared both FA groups. Interestingly, IKDC did not show any clinically significant differences regarding the FA groups. Because the minimum clinically important difference for IKDC is reported to be greater than the Kujala, 16.7 points compared with 8 to 10 points or 10%, respectively, even with a small difference, increased FA group Kujala scores and improvement were clinically and statistically significant whereas IKDC scores were not.39,40 Both questionnaires are well-established evaluation tools; however, the Kujala is more specific for the evaluation of patellofemoral disorder than IKDC. The IKDC is more generic, because it is used for a variety of knee conditions. There are some recently developed specific questionnaires for patellar instability, but they were not applied because they still require language validation. The Kujala was
FEMORAL ANTEVERSION AND PATELLAR INSTABILITY Table 1. Patient Information and Clinical Assessment
Table 3. Influence of FA
Measurements 48 25.22 6.6 36 (75)/12 (25) 9 (18.7) 41.5 11.05 20 (41.67) 1.34 0.52
Patients, n Age, yr, mean SD Sex, female/male (%) Increased FA, n (%) Follow-up, mo, mean SD Patella alta, n (%) Patella cartilage defect size, cm2, mean SD Grade I, n/% Grade II, n/% Grade III, n/% Grade IV, n/% Trochlear dysplasia (Dejour classification), n None Grade A Grade B Grade C Grade D Unavailable
5
5/10.4 16/33.3 17/35.42 10/20.83
0 17 17 7 4 3
FA, femoral anteversion; SD, standard deviation.
designed to document pain in the patellofemoral compartment and probably does not fully capture the subjective difficulties of patients with RPI; however, the Kujala questionnaire is still the most-used questionnaire for RPI.9,44 It is difficult to determine the exact values to define increased FA measured either by physical examination or by image examination. There is no consensus regarding the normal limits or the torsion threshold to indicate surgical correction by derotational osteotomy.18,19,21,27,28,30,31,42 Nevertheless, to successfully determine increased FA, some parameters were defined arbitrarily. The adopted criteria leave no question regarding the presence of this condition, even without the use of CT or magnetic resonance (MR) to confirm it. All 3 adopted criteria were well above the most commonly reported standard values. In addition, the patients had to fulfill all of them, and their reliability already has been proven in previous studies.21,27-32 Also, some of the values were based on
Increased FA Normal FA P Value Patients, n 9 39 Age, yr, mean SD 23.88 6.8 25.53 6.6 .5 Sex, female, n (%) 9 (100) 27 (69) .55 TT-TG, pre-, mean SD 21.33 1.65 20.64 2.21 .37 Patella alta, % 33 44 .42 Follow-up, mo, mean SD 36 8.4 42.76 11.28 .08 Defect size, mean SD 1.22 0.26 1.37 0.57 .74 Outerbridge 4 cartilage 2 (22.22) 8 (20.51) .11 defect, n (%) Trochlear dysplasia, n 9 36 .91 Grade A, % 39 33 Grade B, % 39 33 Grade C, % 14 22 Grade D, % 8 11 Trochlear dysplasia, n 9 36 .35 Low grade (A), % 39 33 High grade (B, C, D), % 61 67 Kujala Preoperatively 56 59.79 .15 Postoperatively 77.7 85.89 .012 Improvement 21.7 26.1 <.001 IKDC Preoperatively 46.21 54.11 .01 Postoperatively 81.43 86.44 .1 Improvement 35.22 32.33 .003 FA, femoral anteversion; IKDC, International Knee Documentation Committee; SD, standard deviation; TT-TG, tibial tubercleetrochlear groove.
Table 2. Function Measured Preoperatively and at Follow-up Measure Kujala Excellent (95) Good (85-94) Fair (65-84) Poor (65) IKDC Tegner SP, n (%) Tegner >5, n (%)
Preoperative 59.08 e e 25% 75% 52.6 5.4 16 (33) 13 (27)
Follow-up 84.37 6% 56% 31% 6% 85.5 5.2 13 (27) 12 (25)
Difference 25.29
32.87 0.15 3 (6) 1 (2)
P Value <.001
<.001 .01 e e
IKDC, International Knee Documentation Committee; SP, sports participation.
Fig 1. Inverted proximal humerus sign. (A) Patient with increased FA; AP radiograph of the right knee showing a bulbous and prominent lateral femoral condyle similar to a humerus head and a small and narrow medial femoral condyle similar to a humerus greater tuberosity; the whole image looks like a inverted proximal humerus. (B) Patient with normal FA; AP radiograph of the right knee showing the classical appearance of more symmetrical condyles with a distinguished medial condyle. (AP, anteroposterior; FA, femoral anteversion.)
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femoral derotation osteotomy from the surgical indications of previous studies.14,16,29,45 Although no CT or MR was used to determine FA, some of the arbitrarily determined values for increased FA also were decided on the basis of image-related research.13-16,18,19,21,41,45 Trochlear dysplasia can have a negative effect on the results of MPFLR used as treatment for RPI, as pointed out by some studies.46-48 Although some studies did not show this negative effect, FA subgroup analysis included the variables that could interfere in the results to eliminate confounders.7,49 Those, presented in Table 3, included trochlea dysplasia individually evaluated by each Dejour type (A, B, C, D) and grouped in low (type A) or high grades (type B, C, D) as previously suggested to improve observer agreement.35 All variables displayed a similar distribution in both groups of FA analysis, validating the statistically significant worst Kujala outcomes and improvement presented in the increased FA group. Also, a recent study demonstrated an important association between increased FA and trochlea dysplasia by the use of several parameters for trochlea morphology analysis and correlating them to the anteversion contribution of the proximal, diaphyseal, and distal portions of the femur.18 This relationship was not found in the present study, a result similar to others, probably because of an insufficiency of trochlear morphology parameters analyzed as proposed by Liebensteiner et al.15,18,50 In the patients with increased FA, a distinct appearance of the knee on the AP radiograph was recognized. The knee was similar to an upside-down proximal humerus with the lateral condyle representing the head and the medial condyle representing a greater tuberosity. Certainly an AP radiograph of the humerus is different, but its similarity was addressed by the authors as the “inverted proximal humerus sign.” This probably happens because the patients with increased FA have a tendency for lateral subluxation of the patella and for increased tilt resulting from internal torsion of the bone. Because the AP radiograph usually is performed with the patella pointing forward, the anterversionrotated appearance of the distal knee makes the lateral femoral condyle more bulbous and prominent and does the opposite to the medial condyle. This sign can be used as a possible indicator of increased FA and should alert surgeons to evaluate it more carefully in some patients. Possibly, the sign is more prominent as FA increases. See Figure 1. No patient reported functional failure (clinical apprehension sign, repeat subluxation, repeat dislocation, subjective instability) postoperatively in contrast to a mean 4.7% to 9.5% incidence at isolated MPFLR without TTO studies and 3% to 10% mean incidence at isolated TTO.10,11,24,51,52 This important difference may be related to the synergic protective function of an
associated MPFLR and TTO procedure. This association may be especially important in cases of severe trochlea dysplasia or important torsional malalignment that are not directly addressed by a trochleoplasty or torsional osteotomy, in addition to TT-TG distances >15 mm.5,8,9,11,51 Limitations The number of patients involved is not large, especially if considering only the subgroup with increased FA. Because of that and low power, there may be other undetected differences between the 2 groups we compared; however, the number is substantial regarding patients with RPI who underwent MPFLR and TTO and even more relevant if considering the small amount of studies involving anteromedialization TTO. Recruitment took 5 years to complete, and the sample size is similar to the majority of studies regarding the same topic.6,7,10,24,53 Nevertheless, the FA subgroup analysis showed statistically significant differences. No CT or MR was used to confirm increased FA, and no objective measurement data were analyzed with the intent to quantify the FA threshold at which derotation osteotomy should be considered. Instead, the FA subgroup analysis was divided in increased or normal FA. Notwithstanding, clinical examination has been used and validated to determine increased FA for a long time and is a reliable approach even today and in patients with cerebral palsy, who comprise much more complex torsional deformities, where the described methods are applied and used as surgical indication and guidance.27,29-32,54 In addition, 3 criteria that used 3 different methods were used to confirm the increased FA.27,30,31 Unfortunately, this study raises some questions but does not answer them regarding what the best surgical procedure is for patients with RPI and increased FA or how much increased FA is acceptable before a derotational osteotomy is indicated. This will be the focus of future studies with better methodology, ideally randomized clinical trials involving derotational osteotomies, MPFLR, and TTO. Nonetheless, the finding that increased FA can have a negative effect in patients with RPI treated with MPFLR and anteromedialization TTO is important to existing knowledge and dictates further investigation of this topic.
Conclusions Increased FA in patients with RPI had a negative effect on anteromedialization TTO combined with MPFLR. Combined anteromedialization TTO and MPFLR had good functional midterm outcomes in treating RPI patients with TT-TG 17 mm.
FEMORAL ANTEVERSION AND PATELLAR INSTABILITY
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