Patellar dislocation occurs when the knee cap slides out of a groove in the thigh bone (femur), typically towards the lateral or outside of the knee. It may spontaneously relocate or have to be manually reduced i.e. put back. This can cause  soft tissue injury to tissues such as the medial patellofemoral ligament and predispose the knee to further episodes of dislocation or subluxation (partial dislocation). Some orthopaedic surgeons, therefore, recommend surgical intervention over non-surgical management.  We found this updated systematic review whose objective was assess the effects (benefits and harms) of surgical versus non-surgical interventions for treating people with primary or recurrent patellar dislocations.

Here’s what they did

As this was an update of a review published in 2011, further searches were carried out in Cochrane Bone, Joint and Muscle Trauma Group’s Specialised Register , Cochrane Central Register of Controlled Trials, MEDLINE , EMBASE , AMED, CINAHL , Health Management Information Consortium, Zetoc , PEDro, Open Grey, WHO Clinical Trials Registry, Current Controlled Trials, UKCRN Portfolio Databases, National Technical Information Service and UK National Research Register Archive up to October 2014. The quality of evidence was assessed by GRADE approach.

Here’s what they found

The database search yielded 714 studies and 181 from trial registers, of these only six matched the inclusion criteria. Outcome measures included: episodes or recurrent dislocation, patient reported pain and physical function, and instability.

• Recurrent dislocation – pooled data from five trials indicated that there was a smaller incidence of recurrent dislocation in the surgical group equating to 104 fewer people per 1000 at 2 and 5 years (RR 0.53, 95% CI 0.33 to 0.87) and 110 fewer people per 1000 at 6 to 9 years (RR 0.67, 85% CI 0.42 – 1.08)
• Kujala patellofemoral disorders score (KPFD) – pooled data from four trials indicated higher (better) scores in the surgical group at 2 – 5 years (MD 13.93, 95% CI 5.33 – 22.53) but favoured non-surgical intervention at 6 – 9 years (MD 3.25, 95% CI 10.61 – 4.11)  although this failed to meet criteria for clinical significance.
• Instability – four studies reported the number of participants suffering episodes of patellar instability (dislocation or subluxation). Pooled data from these studies indicates a reduction in instability in the surgical group at 2 – 5 years (RR 0.44, 95% CI 0.27 to 0.72) and at 6 – 9 years RR 0.80, 95% CI 0.62 to 1.03). However, there was significant heterogeneity between studies.

The authors concluded

‘Although there is some evidence to support surgical over non-surgical management of primary patellar dislocation in the short-term, the quality of the evidence is very low because of the high risk of bias and the imprecision in the effect estimates. We are therefore very uncertain about the estimate of effects’.

Despite some evidence, the authors remain uncertain due to its low quality.

The Musculoskeletal Elf’s view

This review revealed several interesting points. Non-surgical management was poorly described with no indication of type, frequency, duration or intensity of exercise despite previous indications, post studies, that this type of information would be beneficial (Smith, 2010). Considering episodes of recurrent dislocation, only one trial was deemed to be at low risk of selection bias (Petri, 2013) and the results at two years were found to be inconclusive. Although patient reported outcomes (KPFD) favoured surgical intervention at 2 to 5 years, the clinometrics for minimally clinical important difference is based on data for participants with anterior knee pain and not patellofemoral dislocation (Bennell, 2000; Crossley, 2004).

The objective of the review was to assess the effects (benefits and harms) of surgery for primary and recurrent dislocations, but none of the trials identified addressed the latter and only one study reported the frequency of adverse effects (Nikku, 1997).  Having been reliably informed that the surgeons in my neck of the Elf wood almost always offer surgery for recurrent dislocations only, this review, although interesting, does not offer much by way of altering practice in our woodland.

What do you think?

• Do Consultants in your area opt for surgical intervention in primary patellar dislocation?
• What post-operative rehabilitation do you provide? Does this differ from rehabilitation you would offer in conservative cases?

Send us your views on this blog and become part of the ever expanding Musculoskeletal Elf community. Post your comment below, or get in touch via social media (Facebook, Twitter, LinkedIn, Google+).

Links

Hing et al. Surgical versus non-surgical interventions for treating patellar dislocation. Cochrane Database of Systematic Reviews 2011 [Abstract]

Bennell et al. Outcome Measures in patellofemoral pain syndrome: test retest reliability and interrelationships. Physical Therapy in Sports 2000 [Abstract]

Crossley et al. Analysis of outcome measures for persons with patellofemoral pain: which are reliable and valid? Archives of Physical Medicine and Rehabilitation. 2004 [Abstract]

Nikku et al. Operative versus closed treatment of primary dislocation of the patella. Similar 2-year results in 125 randomised patients. Acta Orthopaedica Scandinavica. 1997 [Abstract]

Smith et al. A systematic review of physiotherapy following lateral patellar dislocation. Physiotherapy. 2010.[Abstract]

Petri et al. Operative versus conservative treatment of traumatic patellar dislocation: results of a prospective randomised controlled clinical trial. Archives of Orthopaedic and Trauma Surgery. 2013 [Abstract]

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Wade M CC BY 2.0