Intraobserver and interobserver reliability of the assessment of the patellar articular cartilage in osteoarthritic patients undergoing total knee arthroplasty

Evaluations of radiographic joint space--do they adequately predict cartilage conditions in the patellofemoral joint of the patients undergoing total knee arthroplasty for advanced knee osteoarthritis?

OBJECTIVE

To determine whether assessments of patellofemoral (PF) joint space reliably predict the cartilage conditions in the PF joint of the patients undergoing total knee arthroplasty (TKA) for advanced knee osteoarthritis.

METHODS

Radiographic joint spaces and gross cartilage conditions in the PF joint were assessed in 151 osteoarthritic knees undergoing TKA. Minimum joint space widths (MJSWs) in the medial and lateral compartments of the PF joint were measured separately on Merchant radiographs. Degrees of joint space were graded as normal, narrowed and obliterated, and expected locations of significant cartilage lesions were classified as medial, lateral, and global. Cartilage lesions were grossly assessed in terms of their severity (depth and size) and location. Cross-table analyses and kappa statistics were used to determine the level of agreements between radiographic and gross assessments and the diagnostic accuracies of the radiographic assessments.

RESULTS

The agreements between the radiographic assessments and the gross assessments on the lesion severities and locations were only fair [kappa coefficient (k)=0.288 and 0.211, respectively]. The cross-table analyses demonstrated that 45 (47.4%) of 95 knees with a normal radiographic joint space had moderate or severe cartilage degeneration of the PF joint identified with gross assessments. In the radiographic assessments, the lateral compartment of the PF joint was the most frequent location of joint space narrowing (71.4%) whereas in the gross assessments, the medial compartment of the PF joint was the most frequent location of significant cartilage lesion (48.1%). Diagnostic accuracies on the lesion severities and locations were generally poor.

CONCLUSION

This study demonstrates that prediction of the cartilage conditions of the PF joint by the radiographic joint space can be inaccurate.

Total knee arthroplasty for isolated patellofemoral arthritis in younger patients

Are the results of total knee arthroplasty for isolated patellofemoral osteoarthritis (OA) in younger patients as good as with patellofemoral arthroplasty? We retrospectively compared the outcomes of 33 TKAs in 27 patients with patellofemoral OA younger than 60 years of age (average, 52 years) to those for a matched group of patients with primarily tibiofemoral arthritis. A cemented posterior cruciate ligament-retaining prosthesis was used in 26 of the 27 knees. We recorded the intraoperative condition of the cartilage. Patients were followed a minimum of 2 years (average, 6.2 years). Average Knee Society knee scores improved from 49 preoperatively to 88 at final followup. Average pain scores from 5 to 44 with 29 knees rated with minimal or no pain; two patients reported anterior knee pain. There were no infections, revisions, reoperations, manipulations, patellar instabilities, patellar fractures, or component loosenings. The results in these patients were as good as those for younger historical control patients undergoing patellofemoral arthroplasty and the complication rates lower. The data were similar to those for our matched group of patients with primarily tibiofemoral OA. We believe our data should raise doubts about the use of patellofemoral arthroplasty in any patient.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.