SIGNIFICANCE: Proximal interphalangeal (PIP) joint fusions are necessary to allow for finger strength and utility (Jones, Ackerman, Sammer, & Rizzo, 2011). Currently, there is no surgical protocol dictating the ideal angle for index PIP joint fusion. Fusion angle is dictated by the surgeon’s prior experience, with variable outcomes. An ideal fusion angle will facilitate better occupational therapy treatment outcomes, greater independence in occupational performance, and better quality of life. No studies have evaluated the ideal angle of PIP joint fusion from a functional perspective. Domalain, Evans, Seitz, and Li (2011) investigated the impact of three different PIP fusion angles on the motion of the other joints of the finger and thumb. This study is both novel and critical to ideal fusion outcome for a large body of patients. Will fusion angles have a differential effect on dexterity, pinch strength, and functional performance scores?

RATIONALE: Studies exist regarding optimal PIP joint fusion angle, but they fail to evaluate this from a functional perspective. We test our model and measurement tools for simulated PIP arthrodesis and use functional activity measurements from these subjects to compare “pinch” measurements to functional outcome.

METHOD: This study is a randomized controlled trial of simulated arthrodesis by splinting the index PIP joints of healthy participants at four different angles (30°, 40°, 50°, 60° of flexion). Quantitative evaluation is performed using a VICON 10-camera motion capture system; reflective markers are attached to focal joints on the dominant upper extremity. The Jebsen–Taylor Hand Function Test (Sears & Chung, 2010), Purdue Pegboard (Tiffin & Asher, 1948), and pinch meter are performed without a splint, then the set of tasks are repeated with the index PIP joint splinted at each angle. Initial splint angle is randomized. A custom survey is completed after each set of tasks asking the subject to rate his or her performance on each of the tasks. The subjects are asked to wear the splint, at a randomized angle, for 24 hr and then to complete the shortened Disabilities of the Arm, Shoulder, and Hand (QuickDASH) questionnaire and the Michigan Hand Questionnaire. The study was performed at Stony Brook University’s Rehabilitation Research Movement and Performance (RRAMP) Laboratory. A sample size of 30 participants from students in the Stony Brook Health Sciences Center, between 18 and 30 yr of age, took part in the study. The primary outcome was to find an optimal splint angle based on quantitative evaluation using a VICON motion capture system. Secondary outcomes included rating performances on the Jebsen–Taylor Hand Function Test, Purdue Pegboard, and pinch meter. For statistical analysis, we used the Friedman test and the Wilcoxon signed-rank test. These methods were used because the data sets were assumed to be nonnormally distributed.

RESULTS: The difference between the scores for the splinted and the unsplinted conditions were significant for all tasks except the 50° condition during the pinch strength test. Best mean performance was attained at 40° during the Purdue Pegboard task. Best scores were attained at 50° during pinch.

CONCLUSION: Preliminary performance data suggest that involvement of the pinch appears to be a significant determinant of optimal angle. Splinting the PIP joint had the most impact on tasks requiring fine manipulation and pinch, whereas gross functional tasks were affected least.

Splinting may not have been as debilitating as actual fusion due to some joint motion being preserved within the splint. Although participants’ short-term occupational performance was hindered, this may change over the long term.

Domalain, M., Evans, P. J., Seitz, W. H., Jr., & Li, Z. M. (2011). Influence of index finger proximal interphalangeal joint arthrodesis on precision pinch kinematics. The Journal of Hand Surgery, 36, 1944–1949. http://dx.doi.org/10.1016/j.jhsa.2011.09.010

Jones, D. B., Jr., Ackerman, D. B., Sammer, D. M., & Rizzo, M. (2011). Arthrodesis as a salvage for failed proximal interphalangeal joint arthroplasty. The Journal of Hand Surgery, 36, 259–264. http://dx.doi.org/10.1016/j.jhsa.2010.10.030

Sears, E. D., & Chung, K. C. (2010). Validity and responsiveness of the Jebsen–Taylor Hand Function Test. The Journal of Hand Surgery, 35, 30–77. http://dx.doi.org/10.1016/j.jhsa.2009.09.008

Tiffin, J., & Asher, E. J. (1948). The Purdue Pegboard: Norms and studies of reliability and validity. Journal of Applied Psychology, 32, 234–247. http://dx.doi.org/10.1037/h0061266

Woodworth, J.A., McCullough, M. B., Grosland, N. M., & Adams, B. D. (2006) Impact of simulated proximal interphalangeal arthrodeses of all fingers on hand function. The Journal of Hand Surgery, 31, 940–946. http://dx.doi.org/10.1016/j.jhsa.2006.03.008