Treatments for broken kneecaps in adults

Broken kneecaps (patella fractures) account for 1% of all fractures. There are many treatments for these fractures and they can be treated with surgery or conservatively (any treatment where surgery is not used). Conservative interventions include cast immobilisation, knee brace and immobilisation by traction. Surgery can be open, percutaneous (minimally invasive surgery that uses small incisions) or arthroscopic (using two mini-incisions with the help of an internal camera). The implants used to fix the fracture can be metallic or non-metallic implants, and can be wires, screws, plates, threads, strings, suture buttons, external fixators, rods, nails and combinations of these.

Aim of review

This review aimed to evaluate the effects of different methods for treating kneecap fractures in adults, with or without surgery. The main outcomes we were interested in were patient-rated knee function, knee pain and complications (adverse events).

Search results and quality of the evidence

We searched the scientific literature to January 2020 and found 11 relevant studies with 564 participants. Participants in these studies were aged between 16 and 76 years. There were 340 men and 212 women; the gender of 12 participants was not reported. Seven trials were conducted in China and one each in Finland, Mexico, Pakistan and Turkey. All 11 studies compared different types of surgery or surgical devices. Thus, we found no studies comparing different types of conservative treatment or surgery versus conservative treatment.

The 11 studies made seven comparisons. We judged the evidence available for each comparison was of very low quality. This was mainly because all the trials had design flaws that put them at high risk of bias and the studies were also small with few events.

What the included studies found

None of the studies reported on health-related quality of life, return to previous activity or cosmetic appearance.

We report here the findings for the three most important comparisons.

Four studies compared methods of percutaneous fixation (surgery using small incisions to insert the fixation devices) with open surgery (involving wide incisions). One study found no important difference between the two methods in patient-rated knee function at 12 months. Pooled data showed little difference between groups in knee pain at around two to three months. There were fewer adverse events in the percutaneous group and better observer-rated knee function scores at 12 months.

Two studies compared cable pin system (open or percutaneous surgery) with tension band technique. These found slightly better patient-rated knee function at one year, fewer adverse events and slightly better observer-rated measures of knee function in the cable pin group. There was little important difference between the two groups in knee pain at three months.

Two studies comparing biodegradable (non-metallic) versus metallic implants found little difference in reported outcomes (knee pain, adverse events and knee motion) between the two groups. Neither study reported patient-rated function.

There was very low-quality and incomplete evidence from single trials for four other comparisons.

The very low-quality and incomplete evidence from single trials testing the four other comparisons of different surgical methods meant that we are uncertain of the results for these.

Conclusions

The very low quality of the evidence for the three key comparisons and four other comparisons of difference methods of surgery means that we are uncertain of the findings. Thus, the available evidence is insufficient to draw firm conclusions about the best method of treatment for kneecap fractures. Further research is warranted and should be preceded by research to determine which questions should be prioritised.

Authors' conclusions: 

There is very limited evidence from nine RCTs and two quasi-RCTs on the relative effects of different surgical interventions for treating fractures of the patella in adults. There is no evidence from trials evaluating the relative effects of surgical versus conservative treatment or different types of conservative interventions.

Given the very low-quality evidence, we are uncertain whether methods of percutaneous osteosynthesis give better results than conventional open surgery; whether cable pin system (open or percutaneous surgery) gives better results than the tension band technique; and whether biodegradable implants are better than metallic implants for displaced patellar fractures.

Further randomised trials are needed, but, to optimise research effort, these should be preceded by research that aims to identify priority questions.

Read the full abstract...
Background: 

Fractures of the patella (kneecap) account for around 1% of all human fractures. The treatment of these fractures can be surgical or conservative (such as immobilisation with a cast or brace). There are many different surgical and conservative interventions for treating fractures of the patella in adults. This is an update of a Cochrane Review first published in 2015.

Objectives: 

To assess the effects (benefits and harms) of interventions (surgical and conservative) for treating fractures of the patella in adults.

Search strategy: 

We searched CENTRAL (2020, Issue 1), MEDLINE, Embase, LILACS, trial registers and references lists of articles to January 2020.

Selection criteria: 

We included randomised controlled trials (RCTs) or quasi-RCTs that evaluated any surgical or conservative intervention for treating adults with fractures of the patella. The primary outcomes were patient-rated knee function, knee pain and major adverse outcomes.

Data collection and analysis: 

At least two review authors independently selected eligible trials, assessed risk of bias and cross-checked data extraction. Where appropriate, we pooled results of comparable trials.

Main results: 

We included 11 small trials involving 564 adults (aged 16 to 76 years) with patella fractures. There were 340 men and 212 women; the gender of 12 participants was not reported. Seven trials were conducted in China and one each in Finland, Mexico, Pakistan and Turkey. All 11 trials compared different surgical interventions for patella fractures. All trials had design flaws, such as lack of assessor blinding, which put them at high risk of bias, potentially limiting the reliability of their findings. No trial reported on health-related quality of life, return to previous activity or cosmetic appearance. The trials tested one of seven comparisons. In the following, we report those of the main outcomes for which evidence was available for the three most important comparisons.

Four trials (174 participants) compared percutaneous osteosynthesis versus open surgery. Very low-quality evidence means that we are uncertain of the findings of no clinically important difference between the two interventions in patient-rated knee function at 12 months (1 study, 50 participants) or in knee pain at intermediate-term follow-up at eight weeks to three months. Furthermore, very low-quality evidence means we are uncertain whether, compared with open surgery, percutaneous fixation surgery reduces the incidence of major adverse outcomes, such as loss of reduction and hardware complications, or results in better observer-rated knee function scores.

Two trials (112 participants) compared cable pin system (open or percutaneous surgery) versus tension band technique. The very low-quality evidence means we are uncertain of the findings at one year in favour of the cable pin system of slightly better patient-rated knee function, fewer adverse events and slightly better observer-rated measures of knee function. There was very low-quality evidence of little clinically important between-group difference in knee pain at three months.

Very low-quality evidence from two small trials (47 participants) means that we are uncertain of the findings of little difference between biodegradable versus metallic implants at two-year follow-up in the numbers of participants with occasional knee pain, incurring adverse events or with reduced knee motion.

There was very low-quality and incomplete evidence from single trials for four other comparisons. This means we are uncertain of the results of one trial (28 participants) that compared patellectomy with advancement of vastus medialis obliquus surgery with simple patellectomy; of one quasi-RCT (56 participants) that compared a new intraoperative reduction technique compared with a standard technique; of one quasi-RCT (65 participants) that compared a modified tension band technique versus the conventional AO tension band wiring (TBW) technique; and of one trial (57 participants) that compared adjustable patella claws and absorbable suture versus Kirschner wire tension band.

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