Reconstructed Patellar Tendon Length after Proximal Tibia Prosthetic Replacement

Abstract

A common problem after proximal tibia prosthetic reconstruction is insufficient extensor mechanism or extensor lag. Maintaining the reconstructed patellar tendon length is an important way to minimize extensor lag. We measured the patellar tendon length and extensor lag serially. From 1994-2003, seven consecutive patients with malignant bone tumors of the proximal tibia had prosthetic reconstruction. The extensor mechanism was reconstructed by reattachment of the patellar tendon to the prosthesis with a synthetic material and augmented by a gastrocnemius flap. The patellar tendon length was measured according to the Insall-Salvati ratio. The ratios at 30 degrees knee flexion decreased immediately postoperatively, and reverted to almost the same preoperative values within 18 months. The mean ratios at 60 degrees knee flexion are significantly greater than 30 degrees at 6 months postoperatively. These findings indicate that the patellar tendon stretched, whereas the extensor lag improved continuously for 12 months postoperatively. In the revision at 22 months postoperatively, although the patellar tendon was not reattached to the replaced prosthesis, the ratio and the extensor lag had not worsened. These results show that providing strong continuity of the patellar tendon, gastrocnemius flap, and leg extensors can decrease the extensor lag, although the patellar tendon stretches.

Extensor Function After Medial Gastrocnemius Flap Reconstruction of the Proximal Tibia

“…2 and 4). Shimose et al [37], in a case-series of seven patients, also observed that the patellar tendon stretched during the first few months postoperatively by about the same amount as found in our series. In contrast to our results, the extensor lag improved continuously in that series.…”

“…2) [37]. The Blackburne-Peel Index describes the relationship of the patella to the trochlea by relating the length of the articular surface of the patella to the distance of the inferior patella to the tibial plateau.…”

“…At this location, the patellar tendon often has to be resected together with the tumor [5,24,37]. Many patients with musculoskeletal tumors are young and active, and high cure rates have been reported as a result of the steadily increasing success of chemotherapy after its introduction in the late 1970s [15].…”

“…However, since tendinous tissue does not grow naturally to metal, controversy remains regarding reconstruction techniques for the extensor mechanism [3,5,9,14,20,24,27,[37][38][39][40][41]. Several synthetic devices, such as nonabsorbable tapes, tubes, sutures, cerclage wires, and transplants, such as autograft and allograft from the sartorius or biceps tendons and gastrocnemius flaps have been used [3,5,7,9,14,20,24,31,[37][38][39][40][41].…”

“…Several synthetic devices, such as nonabsorbable tapes, tubes, sutures, cerclage wires, and transplants, such as autograft and allograft from the sartorius or biceps tendons and gastrocnemius flaps have been used [3,5,7,9,14,20,24,31,[37][38][39][40][41]. It has been reported that the patellar ligament stretches after reconstruction with a tumor prostheses and medial gastrocnemius flap, whereas it remains stable when reconstructed with an allograftprosthesis composite [3,37,39]. The patellar height may be measured with various indexes, including the BlackburnePeel index [2,6,8,10,25,28,29,36].…”