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The Effect of Upper Extremity Immobilization on Driving: A biomechanical study
Mark Mildren, MD1; Barth Riedel, MD1; Montri Wongworawat, MD1; Bjorn Harboldt, MD2
Loma Linda University, Loma Linda, CA

Although the impact that lower extremity immobilization has been well studied in the Orthopaedic literature, the effect that upper extremity immobilization has on driving has yet to be elucidated. Furthermore, there is little precedent regarding medical or legal complications of ‘clearing' a patient to drive while the patient is still in an upper extremity cast. We aimed to study the mechanical deficit caused by the immobilization of one of the upper extremities of turning the steering wheel.
We analyzed the turning ability of 8 right handed healthy subjects (average age = 28) using the BTE Simulator 2 (Hanover, MD) both without casts and in single extremity long arm thumb spicas, short arm thumb spica, and short arm cast. Both the left and right arms were casted independently and isometric turning ability tested performing both left and right turns with the hands at neutral, 45 degrees and 90 degrees of both a right and left hand turn. The torque generated at each point was measured. All measurements were performed 3 times. At all hand positions on the wheel, an immobilized upper extremity played a detrimental impact on the ability to generate torque on the steering wheel. Using a repeated measures ANOVA, all positions reached significance (p<0.05) for single arm immobilization with the exception of a left short arm cast (p=0.40). We also found that long arm thumb spica casts have the largest average impact, right arm having a larger deficit than left arm immobilization (71 Nm deficit vs 64 Nm deficit). In contrast to previous studies, we found that right arm immobilization has a consistently greater overall impact on torque generation than the left arm (48 Nm deficit vs 41 Nm deficit).
This is the first study to assess the mechanical detriment that an upper extremity cast plays on a driver's ability to generate torque on a steering wheel throughout a 90 degree turn in either direction. We found that a long arm thumb spica had the largest negative impact on force generation, and that right arm immobilization has a greater deficit than left. The role that this would play in a real life scenario would be contingent on several factors such as tire pressure, steering ratio, etc. A physician must be cautious in clearing a patient for driving with an upper extremity cast as the driver may not experience optimal turning conditions. P47. Revision of the Failed Thumb Carpometacarpal Arthroplasty: A Review of 32. Patients
Loukia K. Papatheodorou, MD1; Gary Lourie, MD2; Deidre Bielicka, MD1; Benjamin Rogozinski, MD3; Issei Komatsu, MD1; Dean G. Sotereanos, MD1
1UPMC, University of Pittsburgh, Pittsburgh, PA; 2The Hand and Upper Extremity Center of Georgia, Atlanta, GA; 3Atlanta Medical Center, Atlanta, GA

Introduction: Revising the failed thumb carpometacarpal (CMC) arthroplasty can be daunting. Although several surgical approaches have been described, none have adequately highlighted the ideal procedure for revising the painful failed thumb CMC arthroplasty. We retrospectively analyzed the outcomes of 32 patients from two experienced surgeons at different institutions who underwent revision surgery for this challenging problem.
Materials & Methods: Thirty-two patients who had failed thumb CMC arthroplasty were included in this study. There were 24 women and 8 men with a mean age of 57.7 years at the time of the revision surgery. The primary reason for revision was pain due to instability or metacarpal subsidence. The revision surgery included soft-tissue interposition with or without ligament reconstruction and distraction pinning. Eight patients required concomitant metacarpal phalangeal joint fusion. Eleven patients required concomitant partial excision of trapezoid for scaphotrapezoid arthritis. All patients were evaluated clinically and radiographically. Functional outcome was assessed with a pain VAS scale, measurement of grip strength, key pinch strength and range of motion.
Results: The mean follow-up was 57 months (range, 24 to 121 months). All clinical parameters demonstrated improvement at final follow-up. Twenty-seven patients (84.4%) achieved good functional results and five patients (15.6%) fair. Pain levels by VAS scale were significantly reduced in all patients after revision surgery from mean preoperative 7.2 to postoperative 0.7. Grip strength significantly increased on average from 17 kg preoperatively to 21.4 kg postoperatively. Mean key pinch strength significantly improved from 3.2 kg preoperatively to 4.6 kg postoperatively. The mean radial abduction significantly improved from 61o before revision surgery to 67o and mean palmar abduction of the thumb significantly improved from 57o to 61o. There was not a significant difference in the functional outcome in regards to the method of revision surgery (soft-tissue interposition alone versus with ligament reconstruction) all in combination with distraction pinning. All patients were satisfied with the revision surgery.
Conclusions: Surgery for failed thumb CMC arthroplasty is successful and provides satisfactory functional results with careful attention to clinical and radiographic details. Revision surgery with soft-tissue interposition with or without ligament reconstruction and distraction pinning for failed CMC arthroplasty of the thumb provides pain relief and improves grip and key pinch strength and range of motion of the thumb.

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