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Long-term Outcomes of Lunate Pyrocarbon Prosthetic Replacement with Intercarpal Tenodesis for Late Kienbock's
Mark Henry, MD, Giselle Kala Henry, HS and Forrest Hal Lundy, BS, Hand and Wrist Center of Houston, Houston, TX

Introduction
In late Kienbock's the lunate is fully fragmented and non-reconstructible. Many patients are averse to wrist fusion or proximal row carpectomy and seek alternatives. Replacing the lunate with a pyrocarbon prosthesis preserves load distribution, avoids carpectomy or fusion, but leaves the wrist intrinsically unstable. We now report the long-term outcomes for the initial cohort of patients stabilized with the previously published first-generation technique.
Materials & Methods
Included were the participants enrolled in the original prospective cohort trial, initiated in 2009, that underwent prosthetic replacement of the lunate with dual bundle scaphoid - triquetrum tenodesis for carpal stabilization. Excluded were 5 patients with whom we were unable to re-stablish contact; all patients contacted participated in the current study. Mean follow-up interval from initial surgery was 9.1 (+/- 1.7) years. There were 5 men and 7 women with a mean age of 43 years (+/- 15). Primary outcomes were Disabilities of Arm Shoulder and Hand (DASH) score, revision or conversion surgery, and wrist range of motion (ROM). With most patients residing out of / across the country, only 5 patients were able to return for office examination and the secondary outcomes of grip strength and radiographs; remote patients were all asked to send in radiographs but only one out of country patient did so.
Results
Mean DASH score was 8.9 (+/- 7.1). No patients reported any additional revision or conversion surgery. Mean wrist flexion was 60 degrees (+/- 14). Mean wrist extension was 45 degrees (+/- 21). Mean grip strength was 32 kg (+/- 7); 75 % of contralateral. Prosthetic subluxation varied from volar translation / extension to dorsal translation / flexion. Ulnar translocation was represented by the lunate / radius covering ratio, mean of 32 % (+/- 7). Mean lateral radioscaphoid angle was 43 degrees (+/- 8). Mean scaphoid to prosthesis diastasis on posteroanterior view was 3 mm (+/- 1). There were no cases of joint space narrowing at the radioscaphoid interface to indicate progression of SLAC arthritis.
Conclusions
The first-generation stabilization technique proved incapable of indirectly controlling sagittal plane prosthetic subluxation. Despite this failure, no loss of radioscaphoid joint space or progression towards SLAC arthritis was seen, consistent with preservation of the lateral radioscaphoid angle and absence of scaphoid to prosthesis coronal diastasis. Clinical outcomes proved more favorable than anticipated, particularly the low patient self-rated DASH scores and the absence of any revision or conversion surgery.


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