Background

Patellar (knee cap) dislocation, characterized by trauma of the surrounding connective tissue with subsequent displacement of the patella out with its normal position, is a common orthopaedic injury seen in children and young adults. The injury is most often sustained during sporting activities, such as football and rugby, due to the likelihood of excessive twisting of the bent knee while the foot is fixed to the ground or from a direct traumatic blow. However, occasionally, it may occur in the absence of trauma, especially in young people who are hypermobile. In many cases, the patella spontaneously returns to its original position with extension of the knee or through manual reduction; however, soft tissue involvement can lead to further episodes of dislocation or subluxation that can subsequently lead to degenerative changes (osteoarthritis) in the affected knee joint.

Primary (first-time) patellar dislocation is traditionally treated conservatively; however, the rate of recurrence and residual symptoms remains high. Nonsurgical treatment, usually provided by physiotherapists, routinely involves exercise-based therapies that aim to restore musculoskeletal control of the patellofemoral joint through muscle strengthening exercises and activities. Surgical interventions are of three main types: proximal soft tissue patellar realignment procedures; osseous (bony) procedures specifically for trochlear dysplasia (anatomical anatomy); and distal patellar realignment procedures.

In recent years, there has been some debate as to which treatment approach would achieve better results in preventing recurrent instability. There is a need therefore to examine the available evidence in order to inform best clinical practice.

Objectives

The objective of this study was to assess the effects (benefits and harms) of surgical versus nonsurgical interventions for treating people with primary or recurrent patellar dislocation.

Interventions/Methods

This review is an update of a previous review (Hing, et al., 2011), which included randomized controlled trials (RCTs) and quasi-randomized designs that compared surgical versus nonsurgical interventions for treating lateral patellar dislocation.

Surgical interventions included any of the following: medial reefing, quadricepsplasty, lateral release, tibial tubercle transfer, Roux-Goldthwait procedures, trochleoplasty, medial patellofemoral ligament repair, or reconstruction. The control intervention included any nonsurgical treatment, or conservative management, that utilized a period of immobilization, bracing or splinting, manual therapy, exercise-based treatments, education and advice, electrotherapeutic modalities, and taping techniques.

Participants included any individual, of any age, with a reported history of patellar dislocation, either primary or recurrent, recorded either by historical account from the participants or by observation by a healthcare professional.

The primary outcomes under investigation included the following:

* Recurrent dislocation;

* Validated patient-rated knee and physical function scores for patellar dislocation outcomes, for example, the Lysholm Knee Score, the Tegner Activity Scale Score, the Hughston Visual Analog Scale (VAS) Score, and the Short Form-12; and

* Specific tool for appraising patellar disorders, for example, the Kujala Patellofemoral Disorder Score.

Results

A total of six trials (five RCTs and one quasi-randomized trial) based in four countries, Brazil (two trials), Finland (two trials), Germany (one trial), and Denmark (one trial), that recruited a total of 344 participants with primary (first-time) patellar dislocation. The mean ages of participants ranged between 19.3 and 25.7 years, with four trials including children, mainly adolescents, as well as adults. Follow-up for the full study populations ranged from 2 to 9 years across the six studies.

There was very low-quality, but consistent, evidence that participants managed surgically had a significantly lower risk of recurrent dislocation following primary patellar dislocation at 2-5 years follow-up (21/162 vs. 32/136; relative risk (RR), = 0.53 favoring surgery; 95% confidence interval (CI) [0.33, 0.87]; five studies, 294 participants). On the basis of an illustrative risk of recurrent dislocation in 222 people per 1,000 in the nonsurgical group, these data equate to 104 fewer (95% CI [149 fewer, 28 fewer]) people per 1,000 having recurrent dislocation after surgery. Similarly, there was evidence of a lower risk of recurrent dislocation after surgery at 6-9 years (RR = 0.67 favoring surgery; 95% CI [0.42, 1.08]; two studies, 165 participants), but a small increase cannot be ruled out. On the basis of an illustrative risk of recurrent dislocation in 336 people per 1,000 in the nonsurgical group, these data equate to 110 fewer (95% CI [195 fewer, 27 more]) people per 1,000 having recurrent dislocation after surgery.

The very low-quality evidence available from single trials only for four validated patient-rated knee and physical function scores (the Tegner Activity Scale Score, the Knee Injury and Osteoarthritis Outcome Score, Lysholm Knee Score, and Hughston VAS Score) did not show significant differences between the two treatment groups.

The results for the Kujala Patellofemoral Disorder Score (0-100: best outcome) differed in direction of effect at 2-5 years follow-up, which favored the surgery group (mean difference [MD] = 13.93 points higher; 95% CI [5.33 points higher, 22.53 points higher]; four studies, 171 participants) and the 6-9 years follow-up, which favored the nonsurgical treatment group (MD = 3.25 points lower; 95% CI [10.61 points lower, 4.11 points higher]; two studies, 167 participants). However, only the 2-5 years follow-up included the clear possibility of a clinically important effect (putative minimal clinically important difference for this outcome is 10 points).

Conclusions

The authors conclude that although they found some evidence to support surgical over nonsurgical management of primary patellar dislocation in the short term, there is a high degree of uncertainty about the estimate of effect due to the very low quality of the evidence. They recommend the need for adequately powered, multicenter, RCTs, conducted and reported to contemporary standards, that also examine people with recurrent patellar dislocation, adverse events, and long-term outcomes.

Implications for Practice

There is insufficient evidence to support a change to current practice in the management of primary and recurrent patellar dislocations; therefore, treatment choice should primarily be guided by individual patient needs.

References