Advances in the staging of musculoskeletal sarcomas and improvements in diagnostic imaging, adjuvant therapy, and neoadjuvant therapy have enabled orthopaedic oncologists to offer limb salvage surgery as an alternative to amputation. The durability and long term function of the reconstructions performed after tumor resection is a major concern, especially in young and physically active patients.1,4,5,10-12,15,18 Resection of the proximal tibia and reconstruction with either an allograft, endoprosthesis, or a combination (composite biologic implant) are the treatments of choice, although technical problems are still high.15 However, without appropriate extensor mechanism reattachment to the graft or prosthesis, long-term stability and limb function are inadequate.
Several methods are used for reconstruction, including nonabsorbable tape or suture, transferring the proximal fibula, a medial gastrocnemius transposition flap, or direct reattachment to a prosthetic reconstruction or allo- graft. 1,3,4,6,10-12,15,16,18 Increased emphasis has been placed on biologic reconstructive alternatives because of concerns involving the durability of prosthetic materials, and the increasing survivorship of patients with sarcomas.4 An advantage of proximal tibia allografts is the ability to reattach host ligaments and tendons to the allograft, accomplishing an anatomical and biological reconstruction of the extensor mechanism.4,6,11
We determined whether patellar tendon length and imaging integrity were maintained, and whether active knee extension was achieved with adequate function with patellar tendon host-donor reattachments in proximal tibia allograft reconstructions.
MATERIALS AND METHODS
We retrospectively reviewed the records of 53 consecutive patients who had a proximal tibia allograft reconstruction in which patellar tendon host-donor reattachments were performed from1990-2002. We excluded 11 patients: four patients had the allograft removed because of recurrence; four patients had early infections; one patient had a fracture of the allograft; and two patients died before 2 years followup. This left 42 patients for review, thirty-three osteoarticular and nine intercalary allografts (Table 1). The patients had a mean followup of 52 months (range, 24-136 months), and the mean age at the time of the reconstruction was 21 years (range, 11-54 years). Twenty patients were women and 22 were men. The primary diagnosis was osteosarcoma in 23 patients, Ewing's sarcoma in seven patients, giant cell tumor (GCT) in seven patients, chondrosarcoma in one patient, adamantinoma in one patient, fibrosarcoma in one patient, recurrent chondroblastoma in one patient, and recurrent osteoblastoma in one patient.
The surgical procedure included resection of the proximal tibia with a wide bone and soft tissue margin, and the insertion of a fresh deep frozen nonirradiated allograft segment sized to the articular surface. We harvested and stored proximal tibia allografts according to a previously reported technique.21 Allo- graft selection was based on a comparison of the radiographs of the patient and donor to achieve the closest anatomical match. After being thawed in a warm solution, the donor bone was cut to the proper length. We performed fixation of the diaphyseal host allograft junction with a compression plate or an intramedullary (IM) nail. If an osteoarticular allograft was performed, the posterior capsule, both cruciate ligaments, both meniscuses, and the medial collateral ligament from the host were attached to the corresponding allograft. If an intercalary allograft was performed, the intraepiphyseal osteotomy site was stabilized with cancellous screws. The host patellar tendon was sectioned during tumor removal. The remaining tendon was reattached to the corresponding tissue of the allograft. We opened the allograft tendon longitudinally to obtain two flaps where the host tendon was inserted. Both donor flaps were overlapped and sutured in full extension with enough tension to ensure proper positioning of the patella relative to the joint (Fig 1). We performed a medial gastrocnemius transposition flap only to provide soft tissue coverage to the proximal tibia allograft, making no attempt to reinforce the extensor mechanism. Antibiotics were given intravenously until the drainage tubes were removed, and no routine anticoagulation therapy was used.
After reconstruction, the knee was placed in full extension and secured with a knee immobilizer or locked hinged postoperative brace. Ice or a cryotherapy device was used to help minimize postoperative swelling and discomfort. Postoperatively, a physical therapist instructed patients on brace use, crutched walking, and quadriceps contractions. The goals during the first postoperative week were to minimize swelling and obtain passive complete extension. Passive flexion exercises were started 2 weeks postoperatively with the goal of obtaining at least 60º of flexion. At 4 weeks postoperatively, active assisted knee motion was initiated until full active extension and 90° of flexion were obtained. Most patients were seen at 1 week, 2 weeks, 1 month, 2 months, and 3 months postoperatively. They were seen every 3 months thereafter until 2 years postoperatively, and then annually. Plain radiographs were taken at every visit starting at 1 month postoperatively.
The preoperative and latest followup radiographs were reviewed. The radiographs were measured using the lateral view of the knee with the Insall-Salvati patellar tendon-patella ratio.13 The preoperative radiographic ratio was compared with the postoperative ratio at minimum of 24 months postoperatively (average, 52 months).
Magnetic resonance imaging (MRI) of the patellar tendon was performed for 19 patients to evaluate signal intensity and tendon continuity.19 In Grade I, a homogeneous low intensity signal within the entire tendon is present. In Grade II, at least 50% of normal tendon signal is present. In Grade III, the tendon exhibits less than 50% normal appearing signal, and in Grade IV there is a diffuse increase in signal intensity with abnormal appearing strand of tendon. The continuity of the patellar tendon reconstruction was recorded in three grades: Grade A, well- defined tendon; Grade B, wavy but continuous tendon contour; and Grade C, nondelineated tendon.
The functional evaluation was performed with use of the revised 30-point functional classification system established by the International Society of Limb Salvage and the Musculoskeletal Tumor Society (MSTS).9 This functional score measures six parameters: pain, function, emotional acceptance, use of walking supports, walking ability, and gait. Each parameter has a value ranging from 0-5 according to specific criteria. The individual scores are added together to obtain an overall functional score (maximum, 30 points), which then is expressed as a percentage of normal. A score of at least 23 points was considered as an excellent functional result, 15-22 points was a good result, 8-14 points was a fair result, and less than 8 points was a poor result.
We measured postoperative range of motion (ROM) and any extensor lag with a handheld goniometer. An extensor lag was defined as the difference between the greatest passive extension and the greatest active extension of the knee.
The Insall-Salvati ratio, magnetic resonance images, extensor lag, and ROM of the knee were investigated serially by two investigators (LAAT, EA) who were blinded to the results.
We compared groups using a paired t test and correlations using Pearson's correlation coefficient. We defined significance as p < 0.05.
Radiographic evaluations showed no proximal patellar migration. The mean original preoperative patellar tendon index was 1.15 ± 0.05 (± 2 standard error [SE]) (range,0.9-1.42). At last followup, the mean reconstructed host- donor tendon index was 1.13 ± 0.07 (± 2SE) (range, 0.76-1.9) (Fig 2).
Magnetic resonance images showed the patellar reattached tendon continuous in all 19 patients (Fig 3). The average time between the reconstruction and the postoperative MRI was 16 months (range, 6-72 months). According the classification for signal intensity there were 11 patients in Grade I, seven patients in Grade II, and one patient in Grade III. The MRI evaluation for fiber continuity showed 13 patients in Grade A and six in Grade B.
Although each allograft survived for at least 2 years, three of the 42 allografts were removed and five patients died of disease 2-5 years after reconstruction (Table 1). At final followup the functional condition of the limb was evaluated in 34 patients.
Active knee extension was restored in all functionally evaluated patients. Active ROM was a mean of 110° (range, 80°-135°). Ten patients had an average residual extensor lag of 6.5° (range, 5°-10°), and 24 patients had no extensor lag.
The average functional score of the 34 available patients was 26.6 points (range, 18-30 points). Function was estimated to be excellent in 29 patients and good in five patients. Twenty-five patients had no functional restrictions, eight patients had restrictions in recreational activities, and one patient had partial disability. Thirty-one patients were enthusiastic about the result and three accepted the result. Thirty-three patients walked without the use of supports and one patient walked with two canes. Twenty- nine patients could walk an unlimited distance, and five patients had some limitations in walking. Twenty-seven patients had no discernible limp, six patients had a minor cosmetic limp, and one patient had a major cosmetic limp.
Survival rates and limb salvage in patients with malignant or aggressive tumors have greatly improved by earlier diagnosis, accurate preoperative staging, and adjuvant chemotherapy.1,4,6,10,11,15,18 Functional longevity of reconstruction at the proximal tibia performed after tumor re- section is a major concern because of difficulties obtaining an appropriate extensor mechanism reattachment to the graft or prosthesis. We hypothesized patellar tendon host- donor reattachments in proximal tibia allografts maintain patellar tendon length and integrity, restoring active extension with adequate function.
We note several limitations related to the retrospective nature of this study in which there is no comparison to other types of reconstructive surgery. However, these are demanding and somewhat individualized surgical procedures for a limited patient population and it would be difficult to compare substantially different techniques at the same institution. In addition, all of the participants were tumor patients, which further diminished the study group due to reasons unrelated to the reconstruction.
Prosthetic replacement is an alternative reconstructive option for patients with tumors about the proximal tibia, but numerous difficulties with extensor mechanism reattachment have been reported.1,3,10,12,15,16 Although active extension could be restored, the extensor lag with this type of reconstruction ranged from 7.5-30°,1,10 with the probability of a residual extensor lag of more than 20° in 9-33% of the patients with direct reattachment,1,12 and between 20-44% in reports using gastrocnemius flap to reinforce direct attachment.3,15 Those studies did not report how many patients had no extensor lag at all.
In contrast to prosthetic reconstructions, allografts may provide the possibility to reattach the host patellar tendon to the allograft, accomplishing an anatomical and biological reconstruction of the extensor mechanism of the knee.4,6,11 Although good and excellent functional results were described,4,6,11 no attempts to evaluate extensor mechanism reconstructions were performed in those previous reports.
Mechanical and physical properties using soft tissue allograft junction have been studied in vivo for extensor mechanism reconstructions after disruptions in total knee arthroplasty (TKA).2,5,7,8,20 After this type of reconstruction, active knee extension was found to be restored with a mean extensor lag of 4°,5,7 with a probability of a residual extensor lag of more than 20° in 11 to 33% of the cases.2,7,8 However in 66% of the patients no extensor lag was found.7,8,20 Tensioning the allograft in full extension yields a higher clinical success rate.5,17 A recent study utilizing medial gastrocnemius flap to restore extensor mechanism, with no use of an allograft, found a postoperative mean extensor lag of 24°, with a residual extensor lag greater than 20° in 4 out of 6 patients.14
In our study, reattachment of patellar tendon host-donor in proximal tibia allograft provided the mechanical support needed for healing without the need of a medial gastrocnemius flap for reinforcement. Radiographic measurements were performed in all patients and showed no proximal patellar migration. The mean original preoperative Insall-Salvati patellar tendon index showed no differences with the mean reconstructed host-donor tendon index. According to MRI studies performed in 19 patients, the patellar reattached tendon was continuous in all patients. At final followup, active knee extension was restored in all 34 evaluated patients with a mean functional MSTS score of26.6 points. Twenty-four patients had no extensor lag, while the remaining ten patients had an average residual extensor lag of 6.5° (range, 5°-10°).
Suturing the overlapped donor flaps may provide a higher contact surface between the donor and the host, which probably contributed to healing. As stability obtained by the reconstruction is high, no cast was used to immobilize the limb. The postoperative rehabilitation included passive flexion exercises started 2 weeks postoperatively, and active assisted knee motion started 4 weeks postoperatively. This postoperative regime allows superior knee extension strength.
The treatment of skeletal deficiencies and the reconstruction of the extensor mechanism after resection of the proximal end of the tibia remains controversial to tumor surgeons. Our data provide evidence patellar tendon host donor healing after proximal tibial allograft reconstruction restores active knee extension. It remained continuous and stable at a mean of 52 months post transplantation. The potential clinical relevance of these findings may be applicable when allogeneic extensor mechanism tissues are used to restore grossly disrupted patellar tendons in failed total knee arthroplasty or due to traumatic defects.
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