AAOS Now

Published 1/1/2010
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Annie Hayashi

Poor outcomes for surgically treated patella fractures

Study shows long-term significant objective and subjective deficits

Patients with patella fractures continue to experience significant pain, reduced range of motion, and muscle deficits at a median of 6.5 years following their surgery, according to the results of a study presented by Christopher T. LeBrun, MD, at the 2009 annual meeting of the Orthopaedic Trauma Association.

Although patella fractures represent only 1 percent of all fractures, “a unified approach and outcome assessment of these injuries remains elusive,” Dr. LeBrun said. “There is a paucity of literature reporting on the follow-up of these fractures, especially on those treated with modern surgical techniques. To date, studies have been conducted with small numbers of patients and outcome measures that have not been validated.”

Even though predictable union rates have been achieved, little is known on how these intra-articular injuries affect health, function, and lower extremity impairment. To assess patient outcomes, Dr. LeBrun and his colleagues used both disease-specific and quality of life measures along with objective testing.

Assessing patients’ functionality
The observational study involved 40 patients (19 men, average age: 52.2 years, and 21 women, average age: 52.4 years) with isolated, unilateral, surgically treated patella fractures who had been prospectively enrolled in a single institution’s orthopaedic trauma registry between 1991 and 2007.

Most (72.5 percent) of the fractures were closed; 20 percent were type I open, 5 percent were type II open, and 2.5 percent were type III open (Table 1.) Fractures were surgically repaired at a mean of 3.5 days after trauma, using one of the following procedures:

  • Standard tension band with k-wires
  • Tension band through cannulated screws
  • Longitudinal anterior banding and cerclage
  • Partial patellectomy

Patients had a minimum of 1 year follow-up with a median follow-up of 6.5 years (range: 1.25 to 17 years). Each patient agreed to return for functional testing. The uninjured knee served as the control for all assessments.

Patients completed two functional outcome questionnaires—the Short Form-36 (SF-36) Physical Component Summary (PCS)/SF-36 Mental Component Summary (MCS) and the Knee Injury and Osteoarthritis Outcome Score (KOOS). In addition, passive range of motion was measured with a goniometer and the presence or absence of an extensor lag was noted. Motion was measured bilaterally.

Patients performed isometric and isokinetic extension exercises at two different angular velocities on the dynamometer—testing both the uninjured and injured knees—to measure muscular strength.

Poor long-term outcomes found
The SF-36 PCS scores were substantially lower than the published normalized population values while the SF-36 MCS scores were not statistically different from the normalized population values at the time of the study follow-up (
Fig. 1, left).

KOOS subscale scores were also significantly lower than published normalized population values (Fig. 1, right).

Dr. LeBrun attributed the lower SF-36 PCS/MCS and KOOS scores for the study group to articular damage.

“Because of the small amount of prepatellar soft tissue and the direct contact with the distal femur, the articular surface of the contact area was likely damaged even with minimal fracture diastasis,” he said.

“Even with excellent fracture repair, the initial articular damage may lead to premature degenerative changes,” he added.

Results from objective testing showed varying degrees of restrictions and deficits. For example, goniometric testing showed that 20 percent of patients had extensor lag greater than 5 degrees, 38 percent had restricted flexion greater than 5 degrees, and 15 percent had restricted extension greater than 5 degrees.

“Objective measurements with dynamometer testing revealed disappointing extensor muscle deficits at a mean of 6.5 years from injury,” said Dr. LeBrun. For example, the injured leg had a mean isometric extension deficit of 26 percent when compared to the uninjured leg.

Isokinetic extension power was also tested with an angular velocity of 90 degrees/second and 180 degrees/second. Mean deficits of 31 percent and 29 percent respectively were noted when the injured leg was compared to the contralateral leg.

Lessons learned
“This study demonstrated that overall long-term functional outcomes after patella fractures are not encouraging,” Dr. LeBrun said.

“Clearly the goal in treating patellar fractures is to restore the extensor mechanism and accurately reduce fracture fragments to minimize additional insults to the articular cartilage,” he continued. “The articular surface is frequently damaged at the time of the injury, however, and this damage may lead to poor functional results, even with excellent fracture repair.

“This information may prove useful when advising patients of likely long-term outcomes and providing comparisons of future treatment methods,” Dr. LeBrun concluded.

Dr. LeBrun has no disclosures to report. His co-authors report the following disclosures: Joshua Langford, MD—Smith & Nephew; H. Claude Sagi, MD—Journal of Orthopaedic Trauma; Stryker; Smith & Nephew; AO; Smith & Nephew, and Synthes.

Annie Hayashi is the senior science writer for AAOS Now. She can be reached at hayashi@aaos.org