New Surgical Technique of Patellar Tendon Reconstruction in TKA Using Achilles Tendon Allograft

Singapore: Patellar tendon rupture is a devastating complication after total knee arthroplasty (TKA), with a prevalence of 0.17%. While the etiology of this condition is multifactorial, this complication is often observed in patients who have multiple previous knee surgeries, numerous co morbidities, and systemic risk factors such as chronic steroid use.

Several techniques to address patellar tendon rupture, including primary repair, and various reconstructive techniques using autograft, allograft, or synthetic extensor meshes have been described.

G. Poon et al. present a modification of the classic Achilles tendon allograft technique for treatment of patellar tendon rupture after TKA.

Surgical technique:

A 74-year-old Chinese female presented to their clinic with sudden-onset left knee pain and loss of extensor function. She had a past medical history of Cushing syndrome from chronic steroid use, and a left TKA with patellar resurfacing was performed for her left knee osteoarthritis with severe varus deformity a month ago.

Physical examination indicated that her left patella had migrated proximally, and a palpable gap below the patella was noted. There was no active knee extension. The knee remained stable on stress testing.

Plain radiography of the left knee showed a high riding patella with no associated fractures. Ultrasonography confirmed the presence of patella tendon rupture with significant tendon retraction.

The previous incision was used, and wide exposure of the entire quadriceps tendon, patella, patellar tendon, and the tibial tubercle achieved. All quadriceps and residual patellar tendon tissue were preserved. Intraoperatively, the patellar tendon was exposed.

A primary suture repair of the patellar tendon was first performed to position the patella before reconstruction with the allograft began. The proximal portion of the tibia was exposed with subperiosteal elevation over the tibia tubercle. Osteotomy was performed on the proximal tibia to create a trapezoidal cavity about 2-cm long by 1.5- cm wide by 1-cm deep, slightly distal and medial to the original insertion of the patellar tendon to preserve the patellar tendon remnant and ensure central patellar tracking. To prepare the allograft, a calcaneal bone block was fashioned to match the shape of the trapezoid cavity, and the tendinous end of the allograft was split into two bundles of approximately 2/3 - 1/3. The calcaneal bone block was press-fitted into the tibial trapezoidal cavity. Three 20-gauge (1 mm in diameter) cerclage wires were placed at the base of this trough and twisted over the press-fit bone block. A transverse tunnel was then made in the quadriceps tendon just proximal to the superior pole of the patella, and the 1/3 portion of the allograft was passed through the tunnel. The remaining 2/3 portion of the Achilles tendon graft was then laid over anterior to the patella and fixed to the patella through drill holes made on the patella using nonabsorbable Ethibond 5 suture. The tendon graft continued proximally and was sutured to the quadriceps tendon with Ethibond 5 using the Krackow suture technique. After fixation of the 2/3 portion, the 1/3 portion of the allograft which was passed through the transverse tunnel was then sutured back onto the lower portion of the allograft to form a loop around the patella with Ethibond 5 sutures. The surgery was performed with the knee kept in strict full extension throughout.

The knee was immobilized in full extension using a functional knee brace postoperatively for 6 weeks with quadriceps isometric exercise having begun immediately under the supervision of a physiotherapist, and the patient was non-weight-bearing on the left knee with a walker. At 6 weeks, active assisted flexion to 40 degrees has begun, with a gradual increase by 10 degrees every week. At 3 months after the surgery, the patient was able to ambulate independently without the use of braces or walking aids. Full flexion of 90 degrees and extension lag of < 10 degrees were achieved.

At the final follow-up visit at 2 years, extension lag was 0 degrees. At 2-year follow-up visit, plain radiographs showed incorporation of the calcaneal bone block with no resorption. A good implant position with no prosthetic loosening and periprosthetic fracture was noted. There were no patellar tendon rerupture or postoperative infections. The patient had good quadriceps muscle strength and was able to climb stairs without aids. She was satisfied with her functional outcome.

The authors concluded that - careful attention to graft preparation and handling, tensioning of the allograft by maintaining full extension intraoperatively, stable graft fixation, and postoperative rehabilitation led to encouraging results in this complex problem.

Key Words: Patellar tendon rupture, Extensor mechanism reconstruction, Achilles tendon allograft, Patellar tendon repair, Total knee arthroplasty

Further reading:

A Modified Surgical Technique of Patellar Tendon Reconstruction in Total Knee Arthroplasty Using Achilles Tendon Allograft

Glenys Poon, Ing How Moo, Kein Boon Poon

Arthroplasty Today 14 (2022) 22-28

https://doi.org/10.1016/j.artd.2021.10.003