Repair of lesser tuberosity osteotomy for shoulder arthroplasty: biomechanical evaluation of the Backpack and Dual Row techniques.

BACKGROUND: Subscapularis dysfunction following total shoulder arthroplasty can result in permanent loss of function. The lesser tuberosity osteotomy (LTO) has been proposed as a method which utilizes bone-to-bone healing to improve subscapularis function. This study evaluates the biomechanical properties of two described techniques for LTO repair. We hypothesized that a Dual Row repair would be stronger and demonstrate less cyclic displacement than a Backpack repair. MATERIALS AND METHODS: Ten matched pairs of cadaveric humeri were dissected, leaving the subscapularis intact, and a lesser tuberosity osteotomy was performed. Matched shoulders were randomized to either a Backpack repair or a Dual Row repair. Repairs were subjected to cyclic loading to 180 N for 500 cycles, followed by ramp-up loading to ultimate failure. Clinical failure was defined as displacement >5 mm after 500 cycles. RESULTS: Displacement after 500 cycles was significantly greater for the Backpack repair (6.9 mm) than for the Dual Row repair (4.6 mm) (P = .007). Most displacement occurred on the first cycle (Backpack, 4.6 mm; Dual Row, 2.1 mm) (P < .001). There was a trend toward a higher clinical failure rate for the Backpack repair (8/10) than the Dual Row repair (3/10). Ultimate tensile strength was significantly greater for the Dual Row repair (632.3 N) than for the Backpack repair (510.9 N) (P = .01). CONCLUSION: The Dual Row technique is significantly stronger and demonstrates less cyclic displacement than the Backpack technique. Clinical studies are needed to determine the impact of LTO repair technique on subscapularis function following shoulder arthroplasty.

Use of an independent skeletal distractor in hip arthroscopy.

Distraction of the hip joint plays an important role in hip arthroscopy by improving visualization of and access to intra-articular structures. Distraction is usually performed by use of a standard traction table and foot plate, with the patient in either the supine or lateral position. Between 1996 and 2005 at our institution, we have used an inexpensive, independent, sterile radiolucent skeletal distractor device to perform hip arthroscopy in the lateral position successfully in 156 cases for a variety of indications and procedures. The device consists of a perineal post, a longitudinal distraction beam, and a telescoping distraction carriage fitted with a screw drive for attachment to a distal femoral K-wire. Skeletal traction is applied against the perineal post through the K-wire via the action of the distraction carriage and fine-tuned with the screw drive, affording excellent visualization of intra-articular structures. The use of this device during hip arthroscopy negates the need for a fracture table, enables the surgeon to remain sterile and still manipulate the traction apparatus intraoperatively, and provides for simultaneous hip and knee flexion to relax the sciatic nerve. Its modular design and small size make hip arthroscopy possible in almost all settings, including outpatient operating rooms.