MENU

SICOT e-Newsletter

Issue No. 55 - April 2013

Worldwide News

Residual pain due to soft tissue impingement after uncomplicated total ankle replacement
Kim BS, Choi WJ, Kim J, Lee JW.
Yonsei University College of Medicine, Seoul, Korea
Bone Joint J 2013;95-B:378-83

Abstract   Introduction: We report the incidence and intensity of persistent pain in patients with an otherwise uncomplicated total ankle replacement (TAR). Arthroscopic debridement was performed in selected cases and the clinical outcome was analysed.   Methods: Retrospective study, comparative case series. Primary end point: Residual ankle pain after arthroscopic debridement. Method of assessment: Visual analogue pain scale (VAS). Secondary end point: Functional outcome. Method of assessment: American Orthopaedic Foot and Ankle Score (AOFAS).   Results: Among 120 uncomplicated TARs, there was persistent pain with a mean visual analogue scale (VAS) of 2.7 (0 to 8). The intensity of pain decreased in 115 ankles (95.8%). Exercise or walking for more than 30 minutes was the most common aggravating factor (62 ankles, 68.1%). The character of the pain was most commonly described as dull (50 ankles, 54.9%) and located on the medial aspect of the joint (43 ankles, 47.3%).   A total of seven ankles (5.8%) underwent subsequent arthroscopy. These patients had local symptoms and a VAS for pain ≥ 7 on exertion. Impingement with fibrosis and synovitis was confirmed. After debridement, the median VAS decreased from 7 to 3 and six patients were satisfied. The median VAS for pain and the American Orthopaedic Foot and Ankle Society score of the ankles after debridement was similar to that of the uncomplicated TARs (p = 0.496 and p = 0.066, respectively).   Summary: Although TAR reduces the intensity of pain, residual pain is not infrequent even in otherwise uncomplicated TARs and soft-tissue impingement is the possible cause.

Research Analysis   Primary research question: What are the prevalence, character and intensity of residual pain after uncomplicated total ankle replacement (TAR) after excluding known causes for pain after TAR such as infection, septic or aseptic loosening, polyethylene dislocation, component mismatch and malalignment.   Secondary research question: What is the outcome for arthroscopic ankle debridement for soft tissue impingement post TAR?    Methodology: Retrospective case series.    Study population: 137 primary TAR in 122 patients (17 TAR excluded due to complications). Only 120 primary TAR in 107 patients was included in final patient cohort. Mean follow up was 40 months post operatively.   Outcome measurement: VAS for pain score, American Orthopaedic Foot and Ankle Society (AOFAS)ankle-hindfoot score and range of motion (ROM).   Statistical analysis: SPSS v19.0. Paired t-test.   Results: Significant improvement in pain intensity (VAS score) and functional outcome (AOFAS ankle –hindfoot score) after TAR in all patients. However, only 29/120 patients were completely pain free which comparably lower than previous reports in the literature. Also, 7 patients with pain on exertion associated with swelling, tenderness and no evident on plain radiograph underwent ankle arthroscopy and debridement for soft tissue impingement. The pain improved after the debridement except for one.

Comment by Syah Bahari

The result of Total Ankle Replacement (TAR) has improved over the last 10 years. However, the results are still not comparable to total hip or knee replacement. Residual ankle pain is among the complaints from patients who had TAR. There are various factors ranging from surgeon’s experience, the choice of implant used and patient selections that are thought to contribute to this problem. Known complications such as deep infection, septic or aseptic loosening, component mismatch or misalignment, polyethylene dislocation, nerve injury causing neuroma and heterothropic bone formation have been reported as a source for the residual pain.

The report of residual ankle pain after TAR from this study was significantly higher than other studies, which are mostly from a centre of excellence or from the designer of the implant. Thus, this report may give a “real picture” of the expectation for patients after TAR when performed outside the centres of excellence.

This study also addresses another possible cause for the residual pain which is impingement. Pain in the medial or lateral ankle, also sometimes referred to as “gutter pain”, is a recognised problem and has been published by Kurup et al (2008) and Barg et al (2011). Ankle impingement can be divided into bony or soft tissue. Diagnosing bony impingement is relatively straightforward but soft tissue impingement is difficult to diagnose as the radiograph is often normal. Unfortunately, this study did not state their algorithm in diagnosing ankle impingement. MRI is unhelpful due to the metal artefact. Ultrasound with diagnostic injection has been reported to be beneficial in diagnosing soft tissue ankle impingement. However, this has never been studied in TAR patients. Thus, in my opinion, diagnosis of soft tissue impingement in TAR patients is a diagnosis of exclusion.

The authors in this study were using arthroscopic debridement to clear the hyperthropic scar tissue and synovium. This technique was also supported by Shirzad et al (2011) and Richardson et al (2012). Potential advantages of an arthroscopic technique are minimally invasive surgery with early patient recovery and return to function. However, one needs to evaluate this technique with caution. It is often difficult to judge arthroscopically how much soft tissue debridement is required as the pathology is often not clear-cut. The reflective surface of the prosthesis may disorientate the surgeon. Risking damage to the prosthesis is also a concern. With an open debridement, one will be able to assess the ankle passive range of motion and may be able to determine how much soft tissue debridement is required. Scranton et al (1992) compared both techniques for ankle impingement in native ankle but no similar study was done in TAR patients. I think a prospective comparative study comparing both techniques is in order to answer these questions.