Radiologische Diagnostik, Beurteilung und Behandlung des patellofemoralen Schmerzes nach primärer Knieendoprothetik

Patellar Tracking in Total Knee Arthroplasty-Influence on Clinical and Functional Outcome

Anterior knee pain is a common problem after primary total knee arthroplasty (TKA). The aim of this study was to find parameters in patellar positioning which influence the clinical and functional outcome after TKA. Included were 59 patients who underwent TKA, of which three patients were treated bilaterally (n = 62 included knees). In a periodical follow-up of up to 5 years, each patient had to answer three questionnaires (HSS, WOMAC, SF-36) and underwent three radiographies of the knee (including merchant view) and a clinical examination, including Range Of Motion (ROM). All radiographs were evaluated by a single observer blinded to clinical data, who collected multiple parameters of sagittal and axial patellar alignment including newly developed methods for measuring patellar shift and tilt. Depending on the measurement results, three groups were built for each parameter and the influence on the outcome was determined. A lateral patellar tilt of more than 4° resulted in lower scores for both the HSS and WOMAC. The rarely investigated patellar facet angle showed a significantly inferior clinical and functional outcome in late follow-up of >24 months if lower than 142°, possibly due to progressive osteosclerotic changes of the patella caused by increased contact stress with corresponding patellar morphology. No significant difference was found for all other parameters. The newly developed method for measuring patellar shift has proven to be a valuable and easy instrument in the postoperative setting.

[Causes and management of patellar instability after total knee replacement : Lateralization, subluxation and luxation]

BACKGROUND

Patellofemoral complications after total knee arthroplasty are responsible for a variety of surgical revisions.

OBJECTIVE

The causes of the various types of instability of the patella are listed in a differentiated way and the importance of clinical and imaging diagnostics as well as preventive strategies are elaborated.

MATERIAL AND METHODS

This article is based on a selective literature search in the PubMed database and on the long-standing experience of the author.

RESULTS

Besides postoperative genu valgum with malalignment of the extensor mechanisms, other risk factors for patellar maltracking are insufficiency of the medial retinaculum, weakening of the vastus medialis muscle, contracture of the quadriceps femoris or tractus iliotibialis muscle, residual valgus deformity after total knee replacement, femoral or tibial malrotation as well as malpositioning of the patella, inappropriate design of the prosthesis and asymmetrical resection of the patella. The causes with respect to incorrect component positioning, faulty preparation of the patella, leg malalignment, inappropriate design of the prosthesis and soft tissue imbalance have to be recognized in order to address the problem in a targeted way. The preferred method of choice in the case of patellofemoral instability after total knee replacement is normally surgery; however, the cause for the instability has to be identified and consequently corrected before surgery. Without a clearly identified cause surgical measures are unrewarding and almost regularly lead to an unsatisfactory outcome.

CONCLUSION

Patella maltracking after total knee arthroplasty is multifactorial and requires an accurate clarification. A surgical revision is only recommended in cases of clearly defined causes of pain or a clearly defined reason for patella malpositioning.

The efficacy of patellar decompression for improving anterior knee pain following total knee arthroplasty without patellar resurfacing

BACKGROUND

Anterior knee pain remains common following total knee arthroplasty (TKA). In this study, we evaluated the efficacy of patellar decompression via drilling for the treatment of anterior knee pain following TKA without patellar resurfacing.

METHODS

A prospective cohort study was performed in 271 consecutive patients who underwent primary total knee replacement with patellar decompression (study group, n = 131) or without decompression (control group, n = 140). The patients were assessed according to the Knee Society rating, clinical anterior knee pain score, and British Orthopaedic Association patient-satisfaction score in each group. Each assessment was performed without the examiner knowing whether the patella had been decompressed. Radiographic evaluations were also performed according to the Knee Society scoring system for functional activity and our own severity grade system for patellofemoral articular change.

RESULTS

There were no adverse events following patellar decompression. The overall prevalence of anterior knee pain was not significantly different between groups (p = 0.71). However, patients presenting pain over grade II after the operation in the study group were statistically low (p = 0.01). The overall postoperative knee scores were higher in the study group, but there were no significant differences between groups (p = 0.0731). Analyses of the radiographs revealed similar postoperative outcomes in both groups of knees.

CONCLUSIONS

As we observed significantly lower rates of anterior knee pain and no patellar complications following patellar decompression via drilling in TKA without patellar resurfacing, we recommend performing patellar decompression in cases of total knee replacement without patellar resurfacing.