Medial patellofemoral ligament reconstruction

Transcription

1 KNEE Medial patellofemoral ligament reconstruction A PROSPECTIVE OUTCOME ASSESSMENT OF A LARGE SINGLE CENTRE SERIES N. R. Howells, A. J. Barnett, N. Ahearn, A. Ansari, J. D. Eldridge From Bristol Royal Infirmary, Bristol, United Kingdom We report a prospective analysis of clinical outcome in patients treated with medial patellofemoral ligament (MPFL) reconstruction using an autologous semitendinosus graft. The technique includes superolateral portal arthroscopic assessment before and after graft placement to ensure correct graft tension and patellar tracking before fixation. Between October 2005 and October 2010, a total of 201 consecutive patients underwent 219 procedures. Follow-up is presented for 211 procedures in 193 patients with a mean age of 26 years (16 to 49), and mean follow-up of 16 months (6 to 42). Indications were atraumatic recurrent patellar dislocation in 141 patients, traumatic recurrent dislocation in 50, pain with subluxation in 14 and a single dislocation with persistent instability in six. There have been no recurrent dislocations/subluxations. There was a statistically significant improvement between available pre- and post-operative outcome scores for 193 patients (all p < 0.001). Female patients with a history of atraumatic recurrent dislocation and all patients with history of previous surgery had a significantly worse outcome (all p < 0.05). The indication for surgery, degree of dysplasia, associated patella alta, time from primary dislocation to surgery and evidence of associated cartilage damage at operation did not result in any significant difference in outcome. This series adds considerably to existing evidence that MPFL reconstruction is an effective surgical procedure for selected patients with patellofemoral instability. N. R. Howells, MRCS, MSc, Specialist Registrar in Trauma and Orthopaedics A. J. Barnett, FRCS(Orth), Specialist Registrar in Trauma and Orthopaedics N. Ahearn, MRCS, Specialist Registrar in Trauma and Orthopaedics A. Ansari, FRCS(Orth), Knee Fellow J. D. Eldridge, FRCS(Orth), Consultant Orthopaedic Surgeon Bristol Royal Infirmary, Upper Maudlin Street, Bristol BS2 8HW, UK. Correspondence should be sent to Mr N. R. Howells; nickrhowells@yahoo.co.uk 2012 British Editorial Society of Bone and Joint Surgery doi: / x.94b $2.00 J Bone Joint Surg Br 2012;94-B: Received 25 November 2011; Accepted after revision 3 May 2012 Chronic patellofemoral instability can be a disabling condition and most commonly affects young patients. 1,2 Primary patellar dislocation has been reported to occur at rates of 5.8 per , with recurrence following conservative management occurring in between 15% and 44%. 1,2 Even without recurrence, a significant proportion of patients continue to struggle with pain and instability after the initial dislocation. 3 Bony abnormalities, including trochlear dysplasia, patella alta, torsional malalignment and patellar dysplasia, can all predispose to recurrent patellofemoral instability. 4 Soft-tissue abnormalities, both static, including torn medial patellofemoral ligament, and dynamic, including weakened vastus medialis obliquus, as well as generalised complaints such as collagen disorders and hypermobility, are also relevant. 4 However, patellofemoral joint malalignment does not cause functional or symptomatic instability in all patients, and in those with symptoms conservative management can be of considerable benefit. Many surgical techniques have been described for those patients who remain symptomatic despite conservative measures. The goal of surgery is to stabilise the patella, restore normal kinematics and optimise load transmission through the joint. The challenge is to identify and understand the relative contribution of bony and soft-tissue abnormalities in order to plan appropriate corrective procedures. 5 The medial patellofemoral ligament (MPFL) has been shown to be the primary static soft tissue stabiliser of the patellofemoral joint; it is always damaged at the time of primary dislocation and it heals poorly. 6,7 Its reconstruction, in the presence of otherwise normal joint morphology, therefore makes intuitive sense and has been shown in cadaver studies to reduce lateral patellar movement significantly. 8 Many techniques have been described in small case series reporting good clinical outcomes. Systematic reviews have concluded that there is emerging evidence that MPFL reconstruction is an effective procedure with favourable outcomes, 9-11 but there remains no consensus on the most appropriate technique or specific determinants of outcome, with larger studies required. This study reports the prospective analysis of clinical outcome following MPFL reconstruction using a standardised autologous hamstring technique in a large single-centre cohort THE JOURNAL OF BONE AND JOINT SURGERY

2 MEDIAL PATELLOFEMORAL LIGAMENT RECONSTRUCTION 1203 Patients and Methods Between October 2005 and October 2010, 219 MPFL reconstruction procedures were performed in 201 patients for patellofemoral instability, either by or under the supervision of the senior author (JDE) using a standardised technique, as described below. Patients undergoing procedures on both knees did so separately, generally with around six months between procedures. Data was collected prospectively and included pre- and post-operative clinical evaluation, radiological assessment, outcome scoring systems and a satisfaction questionnaire. Follow-up is reported for 211 reconstructions in 193 patients (96.3%) with a mean age of 26 years (16 to 49). The mean follow-up was 16 months (6 to 42). A total of 119 procedures were performed in 109 women and 92 procedures in 84 men. Indications for surgery were atraumatic recurrent patellar dislocation in 141 (66.8%) knees, traumatic recurrent dislocation in 50 (23.7%), pain with instability (subluxation) in 14 (6.6%), and a single dislocation with ongoing symptomatic instability in six (2.8%). All patients underwent a pre-operative MRI scan to determine the osteocartilaginous anatomy. Trochlear dysplasia was graded as normal, mild (shallow trochlear groove), moderate (flat surface) or severe (domed trochlear morphology). The integrity of the MPFL was assessed where possible, any associated chondral defects and bone bruising were noted, the tibial tubercle to trochlear groove (TTTG) offset was measured and the patellotrochlear index (a measure of patellar height) was recorded. 12 Moderate trochlear dysplasia was noted in 126 knees (58%), 77 (35%) had mild dysplasia and 16 (7%) had normal trochlear morphology. No patients had severe dysplasia. In the presence of intact articular cartilage and severe dysplasia, trochleoplasty is the appropriate intervention to restore normal anatomy. 13 All patients who underwent surgery for an indication other than recurrent dislocation had MRI evidence of a degree of trochlear dysplasia in addition to symptomatic instability. A total of 34 knees (16%) had some degree of associated patella alta, with a patellotrochlear index < 12.5%. Of these, five (2.4%) had sufficient alta (an index < 0%) and/or complexity of clinical picture from prior surgical intervention to warrant an adjunctive tibial tubercle distalisation (TTD) procedure at the same time as MPFL reconstruction. All of these presented with atraumatic recurrent dislocation and had moderate dysplasia. Of the five, two had undergone previous tibial tubercle realignment procedures at other centres. No patient in this series underwent adjunctive tibial tubercle medialisation (TTM). Accurate assessment of TTTG offset can be difficult in the context of a dysplastic trochlea. Patients with a truly elevated TTTG > 18 are relatively rare. 14 In the senior author s (JDE) practice these patients are treated with a tibial tubercle medialisation and modified Insall-type medial retinacular augmentation 15 rather than MPFL reconstruction, and hence were excluded. During the five-year recruitment period for this study fewer than ten patients underwent this procedure. The median time from primary dislocation to surgery was 91 months (1 to 480); 23 affected knees (11%) had undergone prior arthroscopy, 30 (14%) had undergone previous patellofemoral realignment surgery and 158 (75%) had undergone no previous surgery on the operated knee. Surgical technique. An ipsilateral semitendinosus autograft is harvested and measured. The gracilis tendon is often too short for this procedure. An arthroscopic assessment is performed using standard portals in addition to, importantly, a superolateral portal in order to assess patellar tracking through a full range of movement (Fig. 1). Associated pathology is identified, recorded and if appropriate, addressed. An incision is made at the medial border of the patella and an extrasynovial plane is developed to the femoral attachment. Femoral and patellar tunnel positions are selected based on cadaver findings of the native insertion of the MPFL. 16,17 A single patellar tunnel of the same diameter as the graft is drilled at the junction of the proximal and middle thirds, avoiding a breach of the anterior cortex. The looped graft is passed from medial to lateral and held with the Endobutton suspensory fixation device (Smith & Nephew Inc., Memphis, Tennessee). The femoral tunnel site is selected just proximal and posterior to the medial epicondyle and the drilling guide pin is inserted. The site is assessed for isometry by looping the graft around the guide pin and assessing graft length and tension through a range of movement. An isometric graft will allow the reconstructed MPFL to function in its native fashion, in tension from 0 to 30 of flexion, acting as a check rein to deliver the patella from full extension into the central trochlea, then relaxed during the remainder of flexion. The site is adjusted until isometric before a 7 mm socket is drilled. The two free graft strands are then passed extrasynovially from the patella to the femur and pulled into the femoral tunnel. The graft is tensioned and patellar tracking is again assessed under direct vision via the superolateral arthroscopy portal (Fig. 2). When the tension of the graft is correct, providing optimal patellofemoral tracking, it is secured in the femoral tunnel with a metal 7 mm 25 mm interference screw. Excessive tightening of the graft must be avoided. Patients were permitted to bear full weight as tolerated post-operatively, and underwent a standardised accelerated rehabilitation programme. They were reviewed post-operatively at six weeks, three months, one year and subsequently annually. Outcome was assessed using the International Knee Documentation Committee (IKDC), 18 Kujala score, 19 Oxford knee score (OKS), 20 Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), 21 Fulkerson modification of the Lysholm score, 22 Tegner activity score 23 and Short-Form 12 (SF-12) questionnaire, 24 comprising both a physical (PCS) and mental component score (MCS). Patients were also asked satisfaction questions requiring yes or no responses. Multiple scores were used, as no one score is yet recognised in this patient population. VOL. 94-B, No. 9, SEPTEMBER 2012

3 1204 N. R. HOWELLS, A. J. BARNETT, N. AHEARN, A. ANSARI, J. D. ELDRIDGE Fig. 1a Fig. 1b Arthroscopic images through the superolateral portal of the left knee showing a) patellar subluxation with the knee in early flexion and b) patellar subluxation with the knee in mid flexion. Fig. 2a Fig. 2b Fig. 2c Intra-operative arthroscopic images in the same knee as in Figure 1, following placement and fixation of anatomical medial patellofemoral ligament (MPFL) reconstruction, showing normal kinematics with the knee in a) early flexion, b) mid flexion and c) full flexion. Statistical analysis. The collected data were compiled onto a secure spreadsheet (Microsoft Corp., Redmond, Washington). Statistical tests were performed using the SPSS software package 16.0 (SPSS Inc., Chicago, Illinois). Kolmogorov-Smirnoff tests were performed to assess normality of data, and parametric tests were used accordingly. Independent samples t-tests, one-way analysis of variance (ANOVA) and Pearson s correlation coefficient were used for data analysis where appropriate. A p-value < 0.05 was considered to be statistically significant. Results There have been no recurrent dislocations. There was a statistically significant improvement between available preoperative and post-operative scores for 193 patients (Table I). Follow-up intervals were not as uniform as prescribed owing to clinic time pressures and the distances of travel for the many tertiary referral patients. More than 90% of patients gave positive responses when asked questions regarding satisfaction following surgery, perceived improvement, willingness to repeat if the situation arose, and likelihood of recommending the procedure to others if their condition was appropriate (Table II). Although 147 patients (76.2%; 157 knees (74.4%)) had resumed sporting activities at follow-up, 25 patients (12.9%; 27 knees (12.8%)) had some recurrent symptoms. The complication rate was low, at 3.3%. These comprised a superficial wound infection in two that responded to antibiotics; one patient had a deep vein thrombosis and was anticoagulated; one developed a neuroma at the site of the incision for harvest of the graft; one had a malpositioned patellar tunnel that required immediate revision; and one patient fell sustaining an undisplaced patellar fracture, which healed with non-operative management. The integrity of the graft and patellar stability remained unaffected. In one patient pre-existing patellofemoral osteoarthritis progressed and patellofemoral arthroplasty was required. Comparison of outcome scores for the patients who sustained complications with those who did not revealed no significant differences. THE JOURNAL OF BONE AND JOINT SURGERY

4 MEDIAL PATELLOFEMORAL LIGAMENT RECONSTRUCTION 1205 Table I. Pre- and post-operative outcome scores Mean score (range) * Pre-operative Post-operative p-value IKDC (26 to 64) (18 to 100) < Kujala (29 to 85) (31 to 100) < OKS (11 to 35) (11 to 48) < WOMAC (25 to 92) (25 to 100) Fulkerson (27 to 82) (17 to 100) SF-12 PCS (17 to 53) (17 to 72) SF-12 MCS (29 to 63) (23 to 68) * IKDC, International Knee Documentation Committee; OKS, Oxford knee score; WOMAC, Western Ontario and McMaster Universities osteoarthritis index; SF-12 PCS/MCS, Short-Form 12 physical/mental component score independent t-test Table II. Subjective post-operative satisfaction responses in 211 knees Subjective questionnaires n (%) Are you satisfied with the outcome of the operation? No 14 (6.6) Yes 197 (93.4) Did the operation improve or abolish your symptoms? No 15 (7.1) Yes 196 (92.9) Would you have the same procedure again? No 9 (4.2) Yes 202 (95.9) Would you recommend this procedure to others? No 10 (4.7) Yes 201 (95.3) Have you had a recurrence of your symptoms? No 184 (87.2) Yes 27 (12.8) Have you resumed sport/activity? No 54 (25.6) Yes 157 (74.4) Do you have any residual symptoms? No 127 (60.2) Yes 84 (39.8) In all, 11 patients (5.2%; 11 knees) required further surgery. Of these, five underwent removal of the Endobutton and the following additional procedures were required by one patient each: screw removal for prominence and discomfort; arthroscopic assessment for a medial swelling; arthroscopic partial release for an over-tensioned graft; patellofemoral arthroplasty for progressive osteoarthritis; acute tunnel repositioning due to a malpositioned patellar tunnel; and revision MPFL reconstruction using a Ligament Augmentation Reconstruction System ligament (LARS; Corin, Cirencester, United Kingdom) following persistent symptomatic instability. This patient had dysplasia on the borderline between moderate and severe with some associated chondral damage, had undergone successful contralateral MPFL reconstruction for less marked dysplasia, and was keen for the same procedure again. Unfortunately, the dysplasia was too marked for this procedure to control for instability insufficient to control the instability. Arthroscopic assessment of the patellofemoral articular surface at the time of MPFL reconstruction revealed that 166 (78.7%) knees had no chondral damage, 22 (10.9%) had an osteochondral defect, 17 (8.1%) had grade II/III chondral wear and five (2.4%) had grade IV chondral wear. Analysis of the effect of chondral damage on post-operative outcome following MPFL reconstruction revealed a trend towards worsening outcomes with increasing severity of chondral damage, but no statistically significant differences were found (IKDC, p = 0.27; Kujala, p = 0.32; OKS, p = 0.81; WOMAC, p = 0.87; Fulkerson, p = 0.87; Tegner, p = 0.44; SF-12 PCS, 0.61; SF-12 MCS, p = 0.14; all one-way ANOVA). Analysis of the effect of indication for surgery on outcome revealed no marked trends or statistically significant differences in outcome following a particular indication (IKDC, p = 0.58; Kujala, p = 0.31; OKS, p = 0.75; WOMAC, p = 0.99; Fulkerson, p = 0.58; SF-12 PCS, p = 0.80; SF-12 MCS, p = 0.43; all one-way ANOVA). Similarly, neither the presence nor the severity of trochlear dysplasia (IKDC, p = 0.33; Kujala, p = 0.39; OKS, p = 0.43; WOMAC, p = 0.28; Fulkerson, p = 0.24; Tegner, p = 0.63; SF-12 PCS, 0.49; SF-12 MCS, p = 0.05; all one-way VOL. 94-B, No. 9, SEPTEMBER 2012

5 1206 N. R. HOWELLS, A. J. BARNETT, N. AHEARN, A. ANSARI, J. D. ELDRIDGE Table III. Effect of previous surgery on outcome Score * Prior surgery Mean (SEM) p-value IKDC Yes (n = 55) (2.968) No (n = 155) (1.408) Kujala Yes (2.698) No (1.239) OKS Yes (1.274) No (0.505) WOMAC Yes (2.712) No (0.961) Fulkerson Yes (2.966) No (1.351) Tegner Yes 5.23 (0.298) No 5.36 (0.150) SF-12PCS Yes (1.45) 0.04 No (0.676) SF-12MCS Yes (1.35) No (0.667) * IKDC, International Knee Documentation Committee; OKS, Oxford knee score; WOMAC, Western Ontario and McMaster Universities osteoarthritis index; SF-12 PCS/ MCS, Short-Form 12 physical/mental component score t-test ANOVA) or patella alta (IKDC, p = 0.80; Kujala, p = 0.66; OKS, p = 0.85; WOMAC, p = 0.69; Fulkerson, p = 0.45; Tegner, p = 0.30; SF-12 PCS, p = 0.48; SF-12 MCS, p = 0.72; all one-way ANOVA) was associated with any statistically significant difference in outcome scores. There was a large variation in time from first dislocation to MPFL reconstruction, from one month to 40 years. However, there was no correlation between time from primary dislocation to surgery and outcome (Pearson correlation coefficient (r) = IKDC 0.04, Kujala 0.07, OKS 0.04, WOMAC 0.003, Fulkerson 0.14, Tegner 0.10, SF-12 PCS 0.04, SF-12 MCS 0.05) However, previous surgery did appear to influence outcome. The 55 patients (55 knees) who had undergone previous surgery on the same knee had significantly worse outcomes than those who had not (Table III). Of these, 31 patients (34 knees) had undergone previous realignment procedures, which included 11 lateral releases, 11 tibial tubercle osteotomies, 11 medial reefing/repair procedures and one Roux Goldthwaite procedure. In all, 24 patients (24 knees) had undergone arthroscopy without any documented realignment procedure. Ten patients (4.7%; 11 knees) had comorbidities that are known to be associated with persistent pain and a poor outcomes following surgery. Of these, three had chronic lumbar back pain, three had depression, three had complex regional pain syndrome and one had fibromyalgia. 25 Comparison of outcomes for these patients versus those without such comorbidities revealed statistically significant differences in all but the Tegner score (p = 0.085), with lower scores in the patients with these comorbidities: IKDC p = 0.03; Kujala p = 0.01; OKS p = 0.026; WOMAC p = 0.038; Fulkerson p = 0.002; SF-12 PCS p = 0.004; SF-12 MCS p < Comparison of outcome scores by gender revealed that women had significantly worse outcomes than men (Table IV) and women reported significantly worse subjective responses regarding rates of improvement (p = 0.001), willingness to repeat if the situation arose (p = 0.028), likelihood of recommending the procedure to friends (p = 0.016), rates of recurrent symptoms (p = 0.011), presence of residual symptoms (p = 0.031) and decreased rates of sport resumption (p = 0.026, all chi-squared test). Further analysis revealed that these differences were related to indication, and that differences were only present between men and women undergoing surgery for atraumatic recurrent dislocation. For 25 patients (25 knees) post-operative scores were available at three months and at a mean of 15 months. Statistically significant improvements in IKDC (p = 0.001), Kujala (p = 0.010), OKS (p = 0.044) and SF12 PCS (p = 0.039), and trends towards improvement in the other scoring systems, were seen between these two time points. For 44 patients (44 knees) a minimum of two years follow-up was available (mean 27.9 months; 24 to 42). Outcome scores showed a trend towards further improvement compared to outcomes for the cohort as a whole, but this was not statistically significant. The mean scores in this group were IKDC (SE 2.6), Kujala 85.2 (SE 2.5), OKS 42.8 (SE 1.1), WOMAC 96.7 (SE 1.5), Fulkerson 87.5 (SE 2.1), Tegner 5.7 (SE 0.29), SF-12 PCS 52.3 (SE 1.32) and SF-12 MCS 55.5 (SE 1.26). Discussion Since 1915 over 130 surgical techniques addressing patellofemoral instability and associated pain have been proposed. 10 These include soft-tissue and bony procedures. Direct repair of the MPFL involves injured tendon tissue, and a post-operative re-dislocation rate of 28% was recently reported. 26 Non-MPFL soft tissue techniques have been criticised for disturbing the native patellofemoral biomechanics, with long-term results for lateral release and the Roux Goldthwaite procedure not being uniformly successful. 27,28 A recent systematic review concluded that MPFL reconstruction provides equal or superior functional outcomes to other techniques, with less peri-operative morbidity and fewer complications. 10 A review found that in 28.4% of published studies semitendinosus autograft was the most commonly used soft-tissue reconstruction, 11 but there are variations in the position and number of patellar and femoral tunnels, number of graft bundles and methods of fixation. Despite this, excellent functional outcomes following MPFL reconstruction have been reported but without any consensus on the most appropriate technique or on determinants of outcome THE JOURNAL OF BONE AND JOINT SURGERY

6 MEDIAL PATELLOFEMORAL LIGAMENT RECONSTRUCTION 1207 Table IV. Effect of gender on outcome (p-values calculated by independent t-tests) Outcome score * Gender n Mean (SEM) p-value Atraumatic mean p-value Traumatic mean p-value IKDC Male (1.493) Female (1.928) < Kujala Male (1.395) Female (1.688) < < OKS Male (0.555) Female (0.078) < WOMAC Male (0.865) Female (1.643) Fulkerson Male (1.153) Female (1.987) < < Tegner Male (0.180) Female (0.181) < SF-12 PCS Male (0.708) Female (0.964) SF-12 MCS Male (0.661) Female (0.901) < * IKDC, International Knee Documentation Committee; OKS, Oxford knee score; WOMAC, Western Ontario and McMaster Universities osteoarthritis index; SF-12 PCS/MCS, Short-Form 12 physical/mental component score Regardless of the type of graft or choice of fixation, key principles have emerged from a better understanding of the anatomy and biomechanics of the MPFL that should be adhered to with its reconstruction. Graft isometry is important to allow the reconstructed MPFL to function in its native fashion, in tension from 0 to 30 of flexion, acting as a check rein to deliver the patella from full extension into the central trochlea then remain relaxed during the remainder of flexion. If the femoral insertion is too proximal overload of the medial patellar facet will occur, and if too distal will cause excessive tightness in extension, resulting in nonphysiological patellar movement. 29 Patellar height should be within normal limits to allow correct tunnel positioning and MPFL function, and therefore patellar alta must be corrected if present. The number and position of the patella tunnels should ensure that the patella attachments of the reconstructed graft are centred on the native insertion at the junction of the proximal and middle thirds of the patella and should always be above the midwaist of the patella in order to not over constrain or provide a medial pull to the patella. The native MPFL mechanics are also an important consideration in case selection. In the presence of a domed trochlea there are excessive laterally directed forces beyond those normally supported by a native MPFL. If a reconstructed MPFL is used to resist these forces it will simply result in abnormal joint loading. For this reason trochleoplasty should be undertaken in conjunction with MPFL reconstruction in patients with severe trochlear dysplasia. There is currently no ideal scoring system for patellofemoral instability. It has been proposed that the combination of an anterior knee specific questionnaire with a Tegner activity score and a general health questionnaire provides a comprehensive profile of function in these patients, and therefore these scoring systems were all included in our study. 11,30 If we were to rationalise the scoring systems we used based on experience and degree of correlation with patient satisfaction, we would use IKDC, Kujala, Tegner and SF-12 scores. The complication and re-operation rates were low. However, we acknowledge that although most patients did well, there was a considerable range in postoperative outcome scores. Of particular note was the influence of gender on outcome. Women in our series had significantly lower scores than men. Further analysis revealed that this was specific to patients with atraumatic recurrent dislocation, with no difference between genders for patients with traumatic recurrent dislocations. The difference was independent of all other assessed factors, including length of follow-up, associated comorbidities, hypermobility, previous surgery or time from dislocation to surgery. Nevertheless, the mean outcome in women was still good and provided a significant improvement on their pre-operative function; MPFL reconstruction is therefore still recommended in women with recurrent atraumatic patellar dislocation. Independent of gender, the indication for surgery did not influence the outcome, which suggests that the indications for the procedure we applied were appropriate. The presence or severity of trochlea dysplasia in our series was not found to influence outcome, as also observed previously in a small series by Schottle, Fucentese and Romero. 31 It VOL. 94-B, No. 9, SEPTEMBER 2012

7 1208 N. R. HOWELLS, A. J. BARNETT, N. AHEARN, A. ANSARI, J. D. ELDRIDGE should be noted that in our series this does not include patients with severe trochlear dysplasia, for whom MPFL reconstruction is not felt to be an appropriate procedure. Similarly, the presence of associated patellar alta in our series did not influence the outcome, with only 15% of those with patellar alta having a patellotrochlear index < 0 and therefore requiring an associated tibial tubercle distalisation. Prior surgery to the knee was also identified as a factor associated with significantly worse outcomes. This should be expected, as the previous surgery had often disrupted the normal kinematics of the knee. The presence of patellofemoral articular cartilage damage was associated with poorer post-operative outcomes, but this did not reach statistical significance. This group of patients will need longer follow-up to determine whether the degenerative change will deteriorate with time. Comparison of outcome scores at a mean of three months and 15 months confirmed that patients continue to improve functionally over the first year following surgery. Despite no post-operative dislocations or subluxations, 25 patients (12.9%) did report recurrent symptoms in 27 knees (12.8%). The questionnaires unfortunately do not clarify whether this was pain, instability or both, and so it is difficult to interpret, but it was noted that in this group 21 were female, 12 had undergone previous surgery, 15 had moderate trochlear dysplasia, eight met the criteria for hypermobility, five had comorbidities associated with poor post-operative outcome, and nine had patellofemoral cartilage damage. In summary, we found that MPFL reconstruction using a standardised technique provided significant improvements in all outcome scoring systems, with low complication rates and good patient satisfaction. 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Knee Surg Sports Traumatol Arthrosc 2005;13: THE JOURNAL OF BONE AND JOINT SURGERY