SLR - July 2017 - Kristopher P. Jerry

Ratio of Range of Motion of the Ankle and Surrounding Joints After Total Ankle Replacement

Reference: Dekker, T.J., Hamid, K.S., Easley, M.E., Deorio, J.K., Nunley, J.A. & Adams, S.B. Ratio of Range of Motion of the Ankle and Surrounding Joints After Total Ankle Replacement. J Bone Joint Surg Am. 2017 Apr 5; 99(7), 576–582.

Scientific Literature Review

Reviewed By: Kristopher P. Jerry, DPM
Residency Program: Northwest Medical Center, Margate, FL

Podiatric Relevance: Ankle stiffness is associated with many foot and ankle disorders and functional deficits. Ankle arthroplasty is a progressive method of treating severe ankle arthritis, but it is still unknown how ankle range of motion changes following a total ankle arthroplasty. In this study, the authors tried to identify where motion occurs after total ankle replacement, the difference in range of motion contributions between fixed-bearing and mobile-bearing total ankle replacements and the contribution of abnormal peritalar motion. They hypothesized that sagittal plane radiographic assessment would demonstrate that actual ankle motion through the prosthesis is less than the total arc of ankle motion that may be observed clinically secondary to contributions from adjacent joints.

Methods: A level IV retrospective review of patients enrolled in their prospective total ankle replacement database between May 2007 and October 2015 was conducted. To be included in the study, patients must have undergone a total ankle replacement with a Salto Talaris, STAR or Inbone prosthesis. The patients underwent routine standardized weightbearing maximum dorsiflexion and plantar flexion sagittal radiographs. Sagittal plane ankle and foot measurements were performed on each dorsiflexion and plantar flexion radiograph to determine the total arc of ankle motion, actual ankle motion through the prosthesis, motion through the subtalar and talonavicular joints and midfoot motion. Motion radiographs were routinely made at one year postoperatively and at the time of the most recent follow-up. A minimum follow-up of two years was required of all patients.

Results: There were 197 patients who met the inclusion criteria (75 INBONE, 52 Salto Talaris and 70 STAR prostheses). The mean time to the latest radiographs (and standard deviation) was 42.9 ± 18.8 months. The mean actual ankle motion through the prosthesis was 25.9 degrees ± 12.2 degrees, which was significantly less than the mean total motion arc of 37.6 degrees ± 12.0 degrees. The motion of the ankle accounted for 68 percent of total range of motion, and motion of the peritalar joints accounted for 32 percent. There was no significant difference among the three prostheses or when comparing fixed and mobile-bearing designs for both ranges of motion. However, the mobile-bearing STAR prosthesis demonstrated significantly greater talonavicular joint motion than both the fixed-bearing prostheses. There were no significant changes in any of the measurements from one year to the most recent follow-up.

Conclusions: The authors state that actual ankle motion through the prosthesis was approximately 25 degrees of the total arc of motion. This study also demonstrated that actual ankle motion after total ankle replacement is approximately 12 degrees less than the total arc of motion that might be observed clinically because of increased midfoot and subtalar motion. Even with these findings, the authors believe that arthroplasty still offers the benefit of increased tibiotalar motion and facilitation of a more natural anatomic gait pattern than what other studies have previously described.  

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