Just came back from the surgeon’s office where our 14-year-old daughter was examined for a patellar dislocation (three times now!) and MPFL rupture (MRI results).The surgeon made certain we knew what all the possible complications might be from the surgery (reconstruction of the ligament using her hamstring tendon). One of the biggies was “patellar fracture.” What would cause the knee cap to break during surgery and how likely is that?


Athletes of all ages are at risk for knee injuries, including young children and teens. One of the soft tissue injuries currently under study is the medial patellofemoral ligament (MPFL). This ligament is the main reason the patella (knee cap) stays in front of the knee joint and doesn’t shift off to the side.

Trauma or injury that results in patellar dislocation usually also disrupts the medial patellofemoral ligament (MPFL). And since ligaments don’t heal well on their own, surgery is often needed to repair (or more often) reconstruct the torn tissue. Medial patellofemoral ligament (MPFL) reconstruction is a fairly new procedure.

Reports of complications early after surgery are rare. But recently, a large case series (179 knees) was published. This is the first report of its kind. And although it offers level four evidence (low level), it is still significant in the information offered. One surgeon performed all of the procedures using a single medial-sided patellar tunnel screw fixation.

The tissue graft used to replace the MPFL came from the hamstring tendon. Although there are other graft choices, this is the most commonly used harvest site for the needed tissue. Statistically, 16 per cent of the group had complications. Most of those were major problems (i.e., requiring further treatment, most often another surgery).

The list of both major and minor complications included patellar fracture, hematoma, patellar instability (subluxation or dislocation), poor wound healing, scar formation, pain, reaction to the sutures, blood clots, and complex regional pain syndrome.

Almost half of all complications (47 per cent) for all 179 knees were the result of surgical technical factors. Placement of the tunnel drilled through the bone for the graft and graft tension were the most common technical problems leading to patellar fracture.

The surgeon considered these complications to be the result of improper technique and therefore preventable. The surgeons have already changed their surgical technique based on these outcomes. They may make other changes if/when long-term results indicate the need for further refinements of surgical technique.

Patients who had both knees (MPFL ligament) reconstructed at the same time were at the greatest risk for complications. One other risk factor that was considered statistically significant included gender (females at greater risk than males). Most likely anatomic differences in the shape of the patella contribute to the gender difference.

Age did not seem to be an important variable in the number or type of complications that developed. This information is significant because younger patients who have not completed growth are at risk for growth disturbance with any surgery around the growth plate. There were no cases of growth disturbance observed in this study — at least not in the first three years.