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Background: First-time lateral patellar dislocations have historically been treated with a nonoperative approach; a clinical tool to predict patients who are most likely to redislocate may have clinical utility. Purpose: (1) To determine if there are discriminating factors present between patients who redislocated their patellas and those who did not after a first-time lateral patellar dislocation and (2) to use this information to develop a model that can predict the recurrence risk of lateral patellar dislocation in this population. Study Design: Case-control study; Level of evidence, 3. Methods: The study population included those with first-time lateral patellar dislocation, magnetic resonance imaging within 6 weeks, and 2-year minimum follow-up. Cohort A was from a prospective study with 2-year follow-up. Cohort B was a prospectively identified cohort with retrospective chart review. Follow-up was obtained clinically or via mail for patients without 2-year clinical follow-up. Results: Sixty-one patients (42%) out of 145 with primary lateral patellar dislocation had recurrent dislocation within 2 years. Stepwise logistic regression analysis demonstrated that skeletal immaturity (odds ratio, 4.05; 95% CI, 1.86-8.82; P = .0004), sulcus angle (odds ratio, 4.87; 95% CI, 2.01-11.80; P = .0005), and Insall-Salvati ratio (odds ratio, 3.0; 95% CI, 1.34-6.70; P = .0074) were significant predictors of redislocation. Receiver operator characteristic curves defined the cut points to be sulcus angle ≥154° and Insall-Salvati ratio ≥1.3. The probability of redislocation based on the presence of factors was 5.8% with no factors present and 22.7% with any 1 factor present, increasing to 78.5% if all 3 factors were present. Conclusion: This model demonstrates a high risk of lateral patellar redislocation when a patient presents with skeletal immaturity as well as magnetic resonance measurements of sulcus angle ≥154° and patellar height as measured by Insall-Salvati ratio ≥1.3. A patient will have a low risk of lateral patellar redislocation with the inverse findings.

Background:The surgical management of traumatic patellar dislocations in adolescents is associated with a lower rate of recurrent dislocations compared with nonoperative care. However, the attendant cost of surgery and the quality-of-life benefit of a surgical treatment strategy are unclear.Purpose:To compare the cost-utility of 3 management strategies for acute first-time patellar dislocations in adolescents: (1) nonoperative treatment only, (2) initial nonoperative treatment with surgery only for recurrent dislocations, and (3) immediate surgery.Study Design:Economic and decision analysis; Level of evidence, 2.Methods:A 10-year state-transition Markov model was constructed to compare the cost-utility of the 3 index treatment protocols. Utilities used to define health states were derived from a telephone interview of 60 adolescents with a history of acute patellar dislocations. The probability of transition between each health state was informed by the available literature. Direct costs were estimated using a statewide ambulatory surgery database, and indirect costs were estimated based on parental lost productivity. Effectiveness was expressed in quality-adjusted life years (QALYs). The principal outcome measure was the incremental cost-effectiveness ratio (ICER).Results:In the base case for our model, nonoperative treatment only was the least costly ($7300) but also the least effective (5.30 QALYs); initial nonoperative treatment with delayed surgery cost $10,500 for a 5.93 QALY benefit, while immediate surgical treatment cost $17,100 and provided 6.32 QALY benefits. Compared with nonoperative treatment only, initial nonoperative treatment with delayed surgery was associated with an ICER of $5100 per QALY. When immediate surgery was compared with a strategy of delayed surgery, immediate surgery provided incremental benefits at an ICER of $17,000 per QALY. The model was sensitive to the probability of surgical versus nonoperative treatment to achieve a full return to preinjury activity versus an intermediate lower state. When the probability of achieving a full return to preinjury activity with initial nonoperative treatment exceeds 47.5% (compared with 34.2% in the base case), then initial nonoperative treatment with delayed surgery is preferred to immediate surgery. Similarly, when the probability of achieving a full return to full preinjury activity with surgery falls below 51% (compared with 64% in the base case), then delayed surgery after initial nonoperative treatment is preferred.Conclusion:Immediate surgery and delayed surgical treatment are both cost-effective treatment options; however, immediate surgical treatment provides the highest QALY gains within a 10-year time horizon. Our model sensitivity analysis highlights the role of optimizing functional and quality-of-life benefits in the treatment of acute traumatic patellar dislocations. These findings have implications for clinical guidelines and policy decisions relating to adolescent patellar dislocations.

Background: The incidence of primary lateral patellar dislocation (LPD) in children aged 9 to 14 years is 0.6 to 1.2 per 1000. Causation is assumed to be multifactorial, including anatomic variants of the patellofemoral (PF) joint that result in a higher risk of LPD. No publication has compared the morphology of the PF joint and anatomic patellar instability risk factors (APIFs) in a primary LPD population versus controls, defining children by skeletal maturity. Purpose: To characterize the PF morphology and APIFs (trochlear dysplasia, abnormal lateral patellar tilt, elevated tibial tubercle–trochlear groove [TT-TG] distance, patella alta) through magnetic resonance imaging (MRI) measurements in skeletally immature children with and without a primary LPD and to identify (potential) distinctive differences between these 2 groups. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A prospective series of 103 skeletally immature children aged 9 to 14 years with an MRI-confirmed primary LPD were matched with a control group of 69 children. The PF morphology and APIFs were assessed during a 2.5-year period with standardized MRI using sagittal and axial views. Results: In the LPD group, 79% had 2 to 4 APIFs compared with 7% in the control group. All major measurements of trochlear dysplasia were significantly different between the 2 groups. The mean central condylar height was significantly higher in the LPD group compared with the control group, resulting in a lower trochlear depth (2.3 vs 4.5 mm, respectively) and higher sulcus angle (156.7° vs 141.1°, respectively). The LPD group had significantly higher values of patellar height, Caton-Deschamps index (1.33 vs 1.15, respectively), lateral patellar tilt (21.1° vs 8.5°, respectively), and TT-TG distance (13.9 vs 9.8 mm, respectively) compared with the control group. The main divergent APIF was trochlear dysplasia (defined as trochlear depth Conclusion: There was a significant difference in mean values of all established APIFs between the children with a first-time LPD and the controls. Trochlear dysplasia was the main APIF, and together with lateral patellar tilt (≥20°), they had the strongest association with LPD.

Background: Many factors are involved in causing patellar instability or recurrent patellar dislocations. However, factors affecting the outcomes of anatomic medial patellofemoral ligament (MPFL) reconstruction have not been fully documented. Purpose: To evaluate the rate of recurrent patellar instability after isolated MPFL reconstruction and to elucidate factors affecting the outcomes of isolated MPFL reconstruction using multivariable statistics. Study Design: Case-control study; Level of evidence, 3. Methods: A total of 42 patients (44 knees) who underwent isolated, anatomic MPFL reconstruction using a semitendinosus autograft without any additional patellar stabilization procedures for treating recurrent patellar dislocations were included in this study. All patients were followed for more than 2 years; the mean follow-up period was 3.2 years (range, 2-9 years). Postoperative patellofemoral instability was diagnosed when the patient complained of recurrent patellar subluxations or dislocations or had a positive apprehension sign during follow-up. Preoperative radiographic findings were obtained using plain radiography and computed tomography. Femoral tunnel positions were assessed on postoperative radiographs. The strength of the relationship between postoperative patellofemoral instability and potential risk factors such as preoperative age, sex, body mass index, patellar type, sulcus angle, congruence angle, lateral tilt angle, patellar height, tibial tubercle–trochlear groove (TT-TG) distance, degree of trochlear dysplasia, and femoral bone tunnel position were evaluated by univariate and multivariate logistic regression analyses. Results: At follow-up, 2 knees had experienced a redislocation (4.5%). A positive apprehension sign was still evident in 8 knees (18.2%). Three factors, including the sulcus angle, the congruence angle, and trochlear dysplasia, were extracted by single linear regression analysis. Univariate logistic regression analysis showed that the sulcus angle (odds ratio [OR], 1.11; 95% CI, 1.01-1.22; P = .04) and trochlear dysplasia (OR, 3.04; 95% CI, 1.39-6.63; P = .01) were associated with postoperative patellofemoral instability. Trochlear dysplasia was independently associated with postoperative patellofemoral instability by multivariable logistic regression analysis ( P < .05). An increased TT-TG distance exerted a significant effect on the outcomes of MPFL reconstruction, particularly in patients with type D trochlea. Conclusion: Severe trochlear dysplasia is the most important predictor of residual patellofemoral instability after isolated MPFL reconstruction. In addition, an increased TT-TG distance affected the outcomes in patients with type D trochlea. Additional patellar stabilization procedures should be considered for patients with severe trochlear dysplasia and an increased TT-TG distance.

Background: Previous studies have reported variable rates of recurrent lateral patellar instability mainly because of limited cohort sizes. In addition, there is currently a lack of information on contralateral patellar instability. Purpose: To evaluate the rate of recurrent ipsilateral patellar dislocations and contralateral patellar dislocations after a first-time lateral patellar dislocation. Additionally, risk factors associated with recurrent dislocations (ipsilateral or contralateral) and time to recurrence were investigated. Study Design: Cohort study; Level of evidence, 3. Methods: This population-based study included 584 patients with a first-time lateral patellar dislocation occurring between 1990 and 2010. A retrospective review was conducted to gather information about the injury, subsequent dislocations (ipsilateral or contralateral), and structural characteristics including trochlear dysplasia, patella alta, and tibial tubercle to trochlear groove (TT-TG) distance. Risk factors were assessed to delineate associations with subsequent dislocations and time to recurrence. Results: At a mean follow-up of 12.4 years, 173 patients had ipsilateral recurrence, and 25 patients had a subsequent contralateral dislocation. At 20 years, the cumulative incidence of ipsilateral recurrence was 36.0%, while the cumulative incidence of contralateral dislocations was 5.4%. Trochlear dysplasia (odds ratio [OR], 18.1), patella alta (OR, 10.4), age Conclusion: At 20 years after a first-time lateral patellar dislocation, the cumulative incidence of recurrent ipsilateral patellar dislocations was 36.0%, compared with 5.4% for contralateral dislocations. Trochlear dysplasia, elevated TT-TG distance, patella alta, age

Background:Until now, no study has been published about the electromyographic changes in the extensor apparatus after the Green procedure for proximal realignment in young patients with recurrent patellar dislocations. This electromyographic study was performed to analyze imbalances between the vastus medialis and vastus lateralis muscles after different patellar realignment procedures.Hypothesis:Surgical proximal realignment leads to electromyographic changes in the extensor apparatus of the knee and to imbalances between the vastus medialis and vastus lateralis muscles.Study Design:Cohort study; Level of evidence, 3.Methods:A total of 28 knees of 25 patients, with a mean age of 15 years, were treated operatively for recurrent patellar dislocations. The mean follow-up was 6.3 years. Depending on the type of surgical intervention, the patients were assigned to 3 different groups: the patients of group 1 underwent only the Green vastus medialis obliquus (VMO) advancement, group 2 was treated with a combination of the Green proximal and the Roux-Goldthwait distal realignment, and group 3 was treated with a combination of the Green proximal realignment and an additional tubercle transfer. All patients underwent clinical, radiological, and electromyographic examinations. The muscle activities of a healthy control group without patellar dislocations were used for comparison.Results:A combination of the Green procedure and tubercle transfer led to significantly better clinical results and a lower number of redislocations ( P < .05) compared with patients who underwent only the Green proximal realignment. While ascending or descending stairs, the ratio between the electromyographic activities of the vastus medialis and vastus lateralis muscles in groups 1 and 2 was significantly smaller compared with the control group ( P < .02). Only the electromyograms of group 3 revealed a balanced extensor apparatus during loading with comparable activities of the vastus medialis and vastus lateralis muscles and no significant difference to the control group ( P = .37).Conclusion:Our electromyographic investigations showed the importance of the vastus medialis in the pathogenesis of malalignment of the extensor mechanism. The Green VMO advancement without tibial tubercle transfer is not able to balance the activities of the vastus medialis and vastus lateralis muscles and cannot be recommended for further use.

Background: Trochlear dysplasia is one of the most consistent anatomic factors that can lead to recurrent patellar dislocations. Various trochleoplasty procedures have been described to treat patellar dislocations in high-grade dysplasia by creating a new congruent trochlea. Purpose: To present the midterm efficacy and outcome of the sulcus-deepening trochleoplasty procedure in patients with recurrent patellar dislocations due to high-grade trochlear dysplasia. The clinical evaluation results, the amount of radiological correction, and the prevalence of arthritis were recorded. Study Design: Case series; Level of evidence, 4. Methods: A total of 27 skeletally mature patients (31 knees) with recurrent patellar dislocations due to high-grade trochlear dysplasia without any previous surgery were retrospectively included from September 1993 to September 2006. All patients underwent sulcus-deepening trochleoplasty combined with a bony and/or soft tissue procedure according to concomitant etiological factors to patellar dislocations: medial patellofemoral ligament reconstruction (16.1%), vastus medialis obliquus plasty (83.8%), tibial tuberosity distalization (51.6%), tibial tuberosity medialization (67.7%), and lateral retinaculum release (67.6%). Mean follow-up was 7 years (range, 2-9 years). Results: The mean sulcus angle decreased significantly ( P < .01) from 152° ± 16° preoperatively to 141° ± 9° postoperatively, tibial tuberosity–trochlear groove distance decreased significantly ( P < .001) from 19 ± 4 mm to 12 ± 5 mm, and patellar tilt decreased significantly ( P < .001) from 37° ± 7° to 15° ± 8°. No recurrence was observed, and there was no case of stiffness. Apprehension signs remained positive in 19.3% of the cases, patellar tracking was normal in all cases, and the lateral patellar glide test finding was negative in 96.8%. The mean preoperative International Knee Documentation Committee (IKDC) score was 51 (range, 25-80), and the mean postoperative IKDC score was 82 (range, 40-100) ( P < .001), while the mean Kujala score improved from a preoperative 59 (range, 28-81) to 87 (range, 49-100) postoperatively ( P < .001). There was no radiographic evidence of patellofemoral arthritis at the latest follow-up. Conclusion: Sulcus-deepening trochleoplasty is a valid option for the primary surgical treatment of carefully selected patients with recurrent patellar dislocations with high-grade trochlear dysplasia type B and D. Concomitant etiological factors must be cautiously corrected in an associated procedure. Midterm follow-up showed satisfactory restoration of patellar stability and improvement of knee scores with no complication of subsequent arthritis.

Background:The role of anatomic risk factors in patellofemoral instability is not yet fully understood, as they have been observed in patients either alone or in combination and in different degrees of severity.Purpose:To prospectively analyze rotational limb alignment in patients with patellofemoral instability and in controls using magnetic resonance imaging (MRI).Study Design:Cross-sectional study; Level of evidence, 3.Methods:Thirty patients (mean age, 22.9 y; range, 12-41 y) with a history of patellar dislocation and 30 age- and sex-matched controls (mean age, 25.2 y; range, 16-37 y) were investigated. The patients underwent MRI of the leg at 1.5 T using a peripheral angiography coil and a T2-weighted half-Fourier acquisition single-shot turbo spin echo (HASTE) sequence for measuring femoral antetorsion, tibial torsion, knee rotation, and mechanical axis deviation (MAD). The mean values of these parameters were compared between patients and controls. In addition, the patients underwent an assessment to determine the influence of rotational limb alignment on lateral trochlear inclination, trochlear facet asymmetry, trochlear depth, Insall-Salvati index, and tibial tuberosity–trochlear groove distance.Results:Patients had 1.56-fold higher mean femoral antetorsion (20.3° ± 10.4° vs 13.0° ± 8.4°; P < .01) and 1.6-fold higher knee rotation (9.4° ± 5.0° vs 5.7° ± 4.3°; P < .01) compared with controls. Moreover, patients had 2.9 times higher MAD (0.81 ± 0.75 mm vs −0.28 ± 0.87 mm; P < .01). Differences in tibial torsion were not significant. Also, there were no significant correlations between parameters of rotational alignment and standard anatomic risk factors.Conclusion:Our results suggest that some patients with nontraumatic patellar instability have greater internal femoral rotation, greater knee rotation, and a tendency for genu valgum compared with healthy controls. Rotational malalignment may be a primary risk factor in patellar dislocation that has so far been underestimated.

Background:A patellar dislocation is a common knee injury in the young, athletic patient population. Recent trends indicate that the use of long-term nonoperative treatment is decreasing, and surgical intervention is more commonly recommended for those patients who fail initial nonoperative management with recurrent patellar dislocations. Medial patellofemoral ligament (MPFL) reconstruction has become increasingly utilized in this regard.Purpose:To evaluate outcomes, particularly return to sports and its relationship to postoperative instability, of isolated MPFL reconstruction for the treatment of recurrent patellar dislocations.Study Design:Systematic review and meta-analysis.Methods:A review of the current literature was performed using the terms “medial patellofemoral ligament reconstruction” and “MPFL reconstruction” in the electronic search engines PubMed and EBSCOhost (CINAHL, MEDLINE, SPORTDiscus) on July 29, 2015, yielding 1113 abstracts for review. At the conclusion of the search, 14 articles met the inclusion criteria and were included in this review of the literature. Means were calculated for population size, age, follow-up time, and postoperative Tegner scores. Pooled estimates were calculated for postoperative Kujala scores, return to play, total risk of postoperative instability, risk of positive apprehension sign, and risk of reoperation.Results:The mean patient age associated with MPFL reconstruction was 24.4 years, with a mean postoperative Tegner score of 5.7. The pooled estimated mean postoperative Kujala score was 85.8 (95% CI, 81.6-90.0), with 84.1% (95% CI, 71.1%-97.1%) of patients returning to sports after surgery. The pooled total risk of recurrent instability after surgery was 1.2% (95% CI, 0.3%-2.1%), with a positive apprehension sign risk of 3.6% (95% CI, 0%-7.2%) and a reoperation risk of 3.1% (95% CI, 1.1%-5.0%).Conclusion:A high percentage of young patients return to sports after isolated MPFL reconstruction for chronic patellar instability, with short-term results demonstrating a low incidence of recurrent instability, postoperative apprehension, and reoperations.

Background: A lateral patellar dislocation (LPD) is the most common knee injury in children with traumatic knee hemarthrosis. The medial patellofemoral ligament (MPFL), the important passive stabilizer against LPDs, is injured in more than 90% of cases. The MPFL injury pattern is most often defined in adults or in mixed-age populations. The injury pattern in the skeletally immature patient may be different. Purpose: To describe MPFL injuries in the skeletally immature patient by magnetic resonance imaging (MRI), and to compare the results with the injury pattern found at arthroscopic surgery. Study Design: Case series; Level of evidence, 4. Methods: This was a prospective series of patients aged 9 to 14 years with acute, first-time traumatic LPDs in whom clinical examinations, radiographs, MRI, and arthroscopic surgery were performed within 2 weeks from the index injury. The MPFL injury was divided into 3 different groups according to the location: patellar site, femoral site, or multifocal. The MPFL injury site was confirmed on MRI by soft tissue edema. The length of the MPFL injury at the patellar site was measured at arthroscopic surgery, and those ≥2 cm were defined as total ruptures. Results: A total of 74 patients (40 girls and 34 boys; mean age, 13.1 years) were included; 73 patients (99%) had an MPFL injury according to MRI and arthroscopic surgery. The MRI scans showed an isolated MPFL injury at the patellar attachment site in 44 of 74 patients (60%), a multifocal injury in 26 patients (35%), an injury at the femoral site in 3 patients (4%), and no injury in 1 patient (1%). Arthroscopic surgery disclosed an isolated MPFL injury at the patellar site in 60 of 74 patients (81%) and a multifocal injury in 13 patients (18%); the MPFL injury at the patellar site was a total rupture in 49 patients (66%). Edema at the patellar attachment site on MRI was proven to be an MPFL rupture at the same site at arthroscopic surgery in 99% of the patients. A patellar-based injury, isolated or as part of a multifocal injury, was present on MRI in 95% (n = 70) of the patients, with a false-negative rate of 5% (n = 4) of patients compared with arthroscopic surgery. Conclusion: Skeletally immature children are more prone to sustaining an MPFL injury at the patellar attachment site. Arthroscopic surgery and MRI complement each other in the investigation of MPFL injuries.

Background The tools for measuring the congruence angle with digital radiography software can be difficult to use; therefore, the authors sought to develop a new, easy, and reliable method for measuring patellofemoral congruence. Hypothesis The linear displacement measurement will correlate well with the congruence angle measurement. Study Design Cohort study (diagnosis); Level of evidence, 2. Methods On Merchant view radiographs obtained digitally, the authors measured the congruence angle and a new linear displacement measurement on preoperative and postoperative radiographs of 31 patients who suffered unilateral patellar dislocations and 100 uninjured subjects. The linear displacement measurement was obtained by drawing a reference line across the medial and lateral trochlear facets. Perpendicular lines were drawn from the depth of the sulcus through the reference line and from the apex of the posterior tip of the patella through the reference line. The distance between the perpendicular lines was the linear displacement measurement. The measurements were obtained twice at different sittings. The observer was blinded as to the previous measurements to establish reliability. Measurements were compared to determine whether the linear displacement measurement correlated with congruence angle. Results Intraobserver reliability was above r2 = .90 for all measurements. In patients with patellar dislocations, the mean congruence angle preoperatively was 33.5°, compared with 12.1 mm for linear displacement (r2 = .92). The mean congruence angle postoperatively was 11.2°, compared with 4.0 mm for linear displacement (r2 = .89). For normal subjects, the mean congruence angle was —3° and the mean linear displacement was 0.2 mm. Conclusion The linear displacement measurement was found to correlate with congruence angle measurements and may be an easy and useful tool for clinicians to evaluate patellofemoral congruence objectively.

BackgroundNo data exist whether patients with primary traumatic patellar dislocation benefit from initial arthroscopic medial repair surgery.PurposeTo compare long-term outcomes of patients treated with acute arthroscopic stabilization for patellar dislocation with those treated nonoperatively except for removal of loose bodies.Study DesignCohort study; Level of evidence, 2.MethodsThe study group included 76 consecutive military recruits (72 men, 4 women), with a median age of 20 years (range, 19–22) at the time of dislocation. Thirty patients (group 1) underwent initial arthroscopic medial retinacular repair, and 46 patients (group 2) were treated without stabilizing surgery, including 11 who had osteochondral fragments arthroscopically removed. Patients with previous patellar dislocations or instability were excluded. Aftercare was identical in both groups. Redislocations, subjective symptoms, and functional limitations were evaluated after a median 7-year follow-up.ResultsSixty-one (80%) patients participated in a follow-up examination. At final follow-up, 8 (23%) redislocations occurred in group 2 and 5 (19%) in group 1 ( P = .84). Eight (23%) patients in group 2 and 3 (12%) in group 1 reported patellar subluxations ( P = .18). In group 1, 81% regained their preinjury activity level compared with 56% in group 2 ( P = .05). Functional outcomes were good in both groups (Kujala scores: 87 for group 1 and 90 for group 2) ( P = .22). Regarding the presence of osteoarthritic characteristics in the patellofemoral joint, no statistically significant differences were found between the groups.ConclusionsInitial arthroscopic medial retinacular repair was not followed by improved patellar stability nor reduced incidence of redislocations compared with nonoperative (except for removal of loose bodies) treatment. Acute arthroscopic medial retinacular repair allowed patients to better regain preinjury activity level than in patients not undergoing retinacular repair. The decision to stabilize the patella by initial arthroscopic surgery should be made with caution.

Acute patellar dislocation and relocation produces major forces at the articular surfaces. Articular injury was assessed in 48 patients, 24 boys and 24 girls (mean age, 14 years), with acute, initial, noncontact patellar dislocations. Correlation of the findings of radiographic and arthroscopic examinations was done. Eleven of the 48 patients (23%) had radiologic diagnoses of articular injuries. Thirty-four of the 48 patients (71%) had arthroscopic evidence of articular damage, 32 osteochondral and 2 chondral injuries. Eight of the 28 (29%) arthroscopically identified osteochondral loose bodies (4 to 20 mm) were identified radiologically. Overall, only 11 of the 34 (32%) arthroscopically documented articular injuries were defined by preoperative radiographs. These standard radiographs provided limited information for management decisions. Poor results after patellar dislocation treatment may involve nonrecognition of articular compromise.

Fifty-eight athletically active study participants with 69 knees that had experienced patellar dislocations were available for followup after being selected for a func tional rehabilitation program without antecedent immo bilization. Follow-up evaluation was at a minimum of 24 months after onset of treatment and averaged 46.2 months. Good or excellent results occurred in 39 (66%) knees treated after an initial patellar dislocation and in 15 (50%) knees with a chronic history of patellar insta bility. Twenty-six percent of the 69 knees had experi enced recurrent patellar instability at followup. Overall, 42 patients (73%) were satisfied with their knees after this nonsurgical management. Anatomic predisposition and onset of bilateral instability at an early age were found to be significant factors associated with a less favorable outcome.

Forty patients underwent 45 modified Elmslie-Trillat realignment procedures (mean followup, 2 years) for refractory patellar instability (34 knees) or painful patellofemoral syndrome with malalignment (11 knees). The postoperative congruence angle (mean, +3.4 degrees) was significantly improved compared with the preoperative value (mean, +21.5 degrees). We considered the "normal" congruence angle average as -8 degrees (range, -20 degrees to +4 degrees). Over time postoperatively, we detected no statistical difference in the congruence angle (5 months, 3.4 degrees; 24 months, 6.3 degrees). There were no patellar dislocations postoperatively. Nine knees (20%) had some postoperative subluxation. Ninety-four percent of the patients without subluxation had congruence angles less than 15 degrees, whereas 54% of patients with postoperative subluxation had postoperative congruence angles greater than 15 degrees. The evidence in this study population indicates that the modified Elmslie-Trillat procedure can predictably improve the patellar congruence angle. Adequate correction may eliminate patellar dislocation. Correction of the congruence angle to less than +15 degrees will result in a decreased incidence of postoperative patellar instability. Early full activity postoperatively did not affect the modified Elmslie-Trillat correction of the congruence angle being maintained over time.

Of 27 patients sustaining primary patellar dislocations, 20 were treated with immobilization and subsequent physiotherapy (including nine patients who underwent arthrosocoy) and seven with immediate surgical stabi lization and lateral release. The patients with predis posing factors such as patellofemoral malalignment, abnormal patellar configuration, and a history of prior symptoms of instability were more prone to recurrent dislocation and may benefit from operative intervention. Although the incidence of recurrence among those individuals can be decreased, at least 30% to 50% of all patients having sustained a primary patellar dislo cation will continue to have symptoms of instability and/ or anterior knee pain.

To determine the effectiveness of nonoperative and operative treatment of initial acute patellar dislocation, we reviewed the charts of 399 patients with the diag nosis of an acute dislocation, seen during a 30 year period. One hundred patients (103 knees) met the criteria for inclusion in the study. The average age of the patient at injury was 21.7 years (range, 9 to 72 years). Length of followup aver aged 8 years (range, 2 to 26 years). Retrospectively, we divided the patients into two groups, according to the examination of their unaf fected knee. Group I (69 knees) showed evidence on examination of congenital abnormality of the extensor mechanism in the unaffected knee, indicating a predis position to dislocate with less significant trauma. Group II (34 knees) showed no clinically perceptible congenital predisposition to dislocate based on examination of the unaffected knee. In the nonoperatively treated knees in Group I, there was a 52% (28/54) incidence of good or excellent results. The nonoperatively treated knees in Group II had a 75% (15/20) incidence of good or excellent results. Acute dislocation occurred more frequently in males than in females. Recurrence was rarer in patients whose initial dislocation had occurred when they were over 15 years old. Contrary to recently published reports, primary acute traumatic patellar dislocations can be treated with non operative therapy with good or excellent results. Initial evaluation should include examination of the uninvolved knee which, if found to have signs of congenital abnor mality, would indicate a worse prognosis.