The effect of angled osteochondral grafting on contact pressure: a biomechanical study.

BACKGROUND: Flush osteochondral plugs can reduce contact pressure compared with an empty defect in the articular cartilage. However, incongruities such as graft angulation have an unknown effect. HYPOTHESIS: Incongruity of the articular cartilage after osteochondral transplantation affects articular surface contact pressure. STUDY DESIGN: Controlled laboratory study. METHODS: An 80-N load was applied with a material testing system for 120 seconds to the femoral condyles of 50 fresh swine knees. Contact pressures were measured using Prescale super low film. Five conditions were tested: (1) intact articular surface; (2) surface with 4.5-mm-diameter circular defect; (3) defect grafted with a flush 4.5-mm-diameter plug from the contralateral condyle; (4) defect grafted with a 30 degrees angled 4.5-mm-diameter plug, with lower edge flush (tip elevated with respect to the adjacent surface); and (5) defect grafted with a 30 degrees plug, with tip flush to the adjacent surface (lower edge sunk). Angled grafts were obtained using a rotational bearing vise aligned with a 30 degrees fixed-angle track. The film was digitally scanned and analyzed, and standard statistical tests were performed. RESULTS: Mean peak pressures of intact cartilage (8.57 kg/cm2), flush graft (9.81 kg/cm2), and sunk and angled graft (9.15 kg/cm2) were not significantly different (P < .5). The mean pressures for defects (12.01 kg/cm2) and the elevated angled graft (14.50 kg/cm2) were significantly (P < .05) higher than that of intact cartilage. CLINICAL RELEVANCE: Slightly sunk grafts were still able to reduce elevated contact pressures to normal levels. However, elevated angled grafts increased contact pressure. These results suggest that it is preferable to leave an edge slightly sunk rather than elevated.

Ulnar collateral ligament reconstruction in elite throwing athletes.

PURPOSE: Ulnar collateral ligament (UCL) injuries may result in disabling valgus instability in throwing athletes. We evaluated the docking technique for UCL reconstruction and describe a modification to the technique. METHODS: UCL surgery was indicated in 20 high-level baseball players (13 professional and 7 collegiate) based on medial elbow pain preventing effective throwing, clinically apparent medial elbow laxity, and magnetic resonance arthrogram consistent with UCL injury. The mean age was 21.7 years (range, 17.9 to 25.3 years). One patient had previous UCL reconstruction. One had previous arthroscopic elbow debridement. The mean time between injury and treatment was 73 days. Reconstruction was performed via a muscle-splitting approach and the docking technique with palmaris or gracilis graft. For the initial 12 patients, a 2-strand construct was used; however, during the study period, we developed and began using a 3-strand construct with a double anterior bundle and a single posterior bundle, which was used in the next 8 patients. The ulnar nerve was not routinely transposed unless there were preoperative ulnar nerve symptoms (1 patient). Two patients had osteophyte debridement. One had removal of a loose body. RESULTS: Patients were followed up for a mean of 41.9 months (range, 6.4 to 67.1 months). One player was lost to follow-up and could not be identified on a professional roster. Of the remaining 19 patients, 18 returned to their previous level of participation or higher. Two were occasional pitchers who did not wish to return to pitching but continued to play other positions. They were clinically and functionally asymptomatic. The mean time to return to play was 13.1 months (range, 6.3 to 21.3 months). By use of the Timmerman-Andrews 100-point subjective scoring system, the mean preoperative score was 77.0 (range, 65 to 80) and the mean postoperative score was 98.2 (range, 85 to 100). By use of the Conway-Jobe scoring system, the outcome was rated as excellent in 17 patients and good in 2. One patient underwent subsequent ulnar nerve transposition and returned to the previous level of professional play. CONCLUSIONS: UCL reconstruction with the docking technique is a reproducible and safe operation that can reliably return athletes to a high level of participation with limited adverse effects. LEVEL OF EVIDENCE: Level IV, therapeutic case series.

The effect of graft height mismatch on contact pressure following osteochondral grafting: a biomechanical study.

HYPOTHESIS: Incongruity of the articular cartilage following osteochondral transplantation affects surface contact pressure. STUDY DESIGN: An 80 N load was applied for 120 seconds to the femoral condyles of 10 swine knees. Contact pressures were measured using Fuji prescale film. Seven conditions were tested: (1) intact articular surface; (2) 4.5-mm diameter defect; (3) grafted with 4.5-mm diameter plug elevated 1 mm above adjacent cartilage; (4) plug elevated 0.5 mm; (5) plug flush; (6) plug sunk 0.5 mm below surface; and (7) sunk 1.0 mm. CONCLUSIONS: Peak contact pressures were significantly (P <.001) elevated by approximately 20% after defect creation and were reduced to normal when plugs were flush. There were large and significant (P<.001) increases in pressure with plugs elevated 1 and 0.5 mm. Contact pressures with plugs sunk 0.5 and 1 mm were significantly (P <.01) higher than intact cartilage but were significantly (P <.01) lower than an empty defect. CLINICAL RELEVANCE: Normal contact pressures and patterns can be duplicated with flush articular surface grafts. However, small incongruities, particularly when the plug is elevated, can lead to significantly increased pressure. This reinforces the importance of articular surface congruity in the initial biomechanical state following osteochondral implantation.