Joint distraction for ankle osteoarthritis

4 Efficacy

This section describes efficacy outcomes from the published literature that the Committee considered as part of the evidence about this procedure. For more detailed information on the evidence, see the interventional procedure overview.

4.1 In a randomised controlled trial (RCT) of 36 patients treated by fixed distraction (n=18) or distraction with motion (n=18), the mean combined ankle osteoarthritis scale (AOS) scores (higher score indicates more pain and disability) were 62.8 in the fixed group and 63.1 in the motion group before the procedure. At 104‑week follow‑up, the mean AOS scores were 48.4 in the fixed group and 27.4 in the motion group (significant improvements from baseline in both groups, p<0.01 in the motion group and p<0.02 in the fixed group). A case series of 22 patients treated by ankle joint distraction reported mean (± standard error) percentages of the maximum total AOS score before distraction of 69% (±4%) and 29% (±6%) at a minimum follow‑up of 7 years after distraction (p<0.001). A case series of 25 patients treated by joint distraction reported mean American Orthopaedic Foot and Ankle Society (AOFAS) scores (0 to 100 from worst to best outcomes) of 55 (range 29 to 82) before the procedure and 74 (range 47 to 96) at a mean follow‑up of 30.5 months (significant difference from baseline, p=0.005).

4.2 The case series of 22 patients reported mean (± standard error) percentages of the maximum score for pain measured by clinical evaluation before distraction of 78% (±3%), and of 30% (±5%) at a minimum follow‑up of 7 years after distraction (n=16; p<0.0001). The same study reported mean percentages of the maximum score for AOS scores for pain of 67% (±6%) before distraction and of 25% (±6%) at a minimum follow‑up of 7 years after distraction (n=16; p<0.002). A case series of 26 patients treated by ankle joint distraction reported AOS pain scores (mean percentage of the maximum score ± standard deviation) of 60% (±3%) at baseline, 35% (±4%) at 1‑year follow‑up and 35% (±5%) at 2‑year follow-up (p<0.001 for all scores compared against baseline). The case series of 25 patients reported mean AOFAS pain scores of 15 (range 0 to 20) before the procedure and 31 (range 20 to 40) at a mean follow‑up of 30.5 months; 91% (21/23) of patients reported a reduction in pain.

4.3 The case series of 22 patients reported mean (± standard error) percentages of the maximum score for functional ability measured by clinical evaluation of 20% (±4%) before distraction and 73% (±6%) at a minimum follow‑up of 7 years after distraction (n=16; p<0.001). For the AOS scores for disability the same study reported mean percentages of the maximum score before distraction of 74% (±5%), and of 32% (±7%) at a minimum follow‑up of 7 years after distraction (n=16; p<0.001). In a case series of 23 patients treated by ankle joint distraction, at a mean follow‑up of 64 months after the procedure, 77% (14/18) of patients said that they walked for pleasure, 33% (6/18) of patients said that they could run, 22% (4/18) of patients used an assistive device to walk and 11% (2/18) of patients reported severe limitations in walking ability (no further details provided). The case series of 26 patients reported AOS disability scores (mean percentage of the maximum score ± standard deviation) of 67% (±2%) at baseline, 46% (±5%) at 1‑year follow‑up and 36% (±5%) at 2‑year follow‑up (p<0.001 for all scores compared against baseline). The case series of 25 patients reported ranges of motion before the procedure of 7º dorsiflexion (range –5º to 15º) and 32º plantarflexion (range 15º to 50º), and at a mean follow‑up of 30.5 months of 4.3º dorsiflexion (range 0º to 10º) and 33º plantarflexion (range 20º to 40º); levels of significance were not stated.

4.4 In the RCT of 36 patients treated by fixed distraction or distraction with motion, the motion group had better SF‑36 physical component summary scores than the fixed group at 26 weeks after fixator removal (p=0.02) and at 104 weeks after fixator removal (p=0.05), but not at 52 weeks after fixator removal (p=0.49).

4.5 In the case series of 23 patients, at a mean follow‑up of 64 months, 61% (11/18) of patients were very satisfied or satisfied by the result of the procedure and 71% would recommend this procedure to a friend (absolute number not given), but 33% (6/18) were not satisfied with the outcome.

4.6 A case series of 57 patients treated by ankle joint distraction reported that 23% (13/57) of patients withdrew from the study because of persistent pain; 62% (8/13) of these patients withdrew within 1 year after distraction. All the patients who withdrew were treated by arthrodesis. A combined analysis of treatment failure in a case series of 75 patients treated by ankle joint distraction and in the RCT of 36 patients treated by fixed ankle distraction or distraction with motion, reported treatment failure in 17% (18/105) of patients still included in the studies within 2 years after ankle distraction (6 patients were lost to follow‑up). Treatment failure was defined as patients treated by arthrodesis, osteotomy or a second distraction, or patients who developed Sudeck's atrophy. In a 5 to 10‑year follow‑up study of 29 patients from the RCT of 36 patients, conversion was reported in 45% (13/29) of patients; 28% (8/29) were treated by ankle arthrodesis and 17% (5/29) by total ankle arthroplasty. Of the 13 conversions, 2 were done within 1 year after ankle distraction, 3 in the second year, 1 in the third year, 1 in the fifth year, 3 in the sixth year, 2 in the seventh year and 1 in the eighth year.

4.7 The case series of 25 patients reported that there was no change from baseline in ankle joint space measured on X‑ray, at a mean follow‑up of 30.5 months, in 91% (21/23) of patients.

4.8 The specialist advisers listed the following key efficacy outcomes: improvement in symptoms, reduced pain, improvement in function, preservation of the joint, avoiding or delaying the need for ankle fusion or arthroplasty, preservation or improvement of the range of ankle movement, long‑term increase in joint space measured on X‑ray, and reduced use of analgesics.