Management of Extensor Mechanism Deficit as a Consequence of Patellar Tendon Loss Malhotra et al 1147 Table 1. Clinical and Demographic DataPatient 1 2 3 4Age (y) 68 71 63 69Sex Male Female Female FemaleExtensor lag (degrees) 40 45 40 30Other clinical findings Genu recurvatum Genu recurvatum Valgus laxity of 15°, genu recurvatum Genu recurvatumAssociated medical comorbidities Obese, hypertensive Rheumatoid arthritis Obese, hypothyroid, hypertensive DiabeticPrior surgical treatment Primary repair Primary repair Primary repair followed by Primary repair augmentation with semitendinosusPostulated cause of patellar Extensive release Extensive release Distal realignment with lateral release Difficult exposure tendon rupturewith patella–patellar tendon–tibial tubercle allograft augmentation with tendon grafts, was discussedcounting exclusively on extrapolative bone-to-bone with all of the patients. None of the patients hadhealing, which is more predictable. clinical or laboratory evidence of infection. On physical examination, the following variables Materials and Methods were recorded: active and passive range of motion, presence or absence of extensor lag, extensor Consecutive reconstructions with extensor mechanism tracking, as well as neurovascularmechanism allograft in 4 patients (3 women and 1 status. The tracking of the extensor mechanismman) were under taken by the surgeon (RM) in the during range-of-motion testing was examined clo-institute. The clinical and demographic data of all 4 sely and was found to be normal. There was no distalpatients are shown in Table 1. neurovascular deficit in any of the patients. All knees had a failed extensor mechanism All but 1 patient had revision total knee arthro-associated with a total knee arthroplasty. One plasty at the time of extensor mechanism recon-patient had a prior failed direct repair and again a struction because of associated aseptic loosening orfailed extensor mechanism repair augmented by component malrotation. Implants were retained,semitendinosus autograft. The other 3 patients had and the polyethylene was changed in the fourthfailed primary repair. Nonoperative treatment, patient during extensor mechanism reconstruction.including bracing as well as other operative options, The patients were observed for a mean ofincluding additional attempt at direct repair and 21 months, ranging from 14 to 30 months. ClinicalFig. 1. A and B, Intraoperative and schematic diagram showing preparation of donor allograft and creation of ridge onundersurface of patella.
1148 The Journal of Arthroplasty Vol. 23 No. 8 December 2008 Fig. 2. Intraoperative (A) and schematic diagram (B) showing creation of trough in host patella.and radiographic examination was performed at 6 remained in the central portion, on either sideand 12 weeks, 6 months, 1 year, and every year of which the cancellous surface was exposedthereafter. Active and passive range of motion, (Fig. 1A and B).along with extensor lag, were recorded at an eachfollow-up. The knee was graded in accordance with Preparation of Host Patellar Troughthe 100-point system of the Hospital for Special We divided the host patella in midline long-Surgery (New York, NY), preoperatively and post- itudinally and removed some bone on either sideoperatively, beginning at 3 months. A score of more with the help of an oscillating saw to create a troughthan 84 points is considered an excellent result; 70 of a width of 1 cm (Fig. 2A and B). The allograftto 84 points, a good result; 60 to 69 points, a fair patella with a ridge created on its articular surfaceresult; and less than 60 points, a poor result. was then fitted/fixed into this trough (Fig. 3A and B) and secured with the help of screws insertedSurgical Technique horizontally, going from host bone to allograft to Allograft Preparation. Simultaneous with the host bone.revision or placement of the total knee arthroplastycomponents, the patella–patellar tendon–tibial Preparation of the Host Proximal Tibial Troughtubercle allograft was prepared on the back table.We first marked with a marking pen over the tibial We created a trough in the proximal portion oftubercle and proximal part of the allograft tibia and the tibia as recommended [9,10]. The allograftplanned harvest of the allograft tibial bone block, in tibial tubercle was then inserted into the host tibiala rectangular fashion. With the use of a small thin trough and was gently press-fit with a bone tampmicrosagittal saw, the allograft block was harvested or punch, in an “up and in” fashion, to lock thefrom the allograft tibia, with careful attention so as graft in place. This graft was then secured with thenot to damage the allograft patellar tendon. help of wires. Once the allograft was secured, Next, we cut the articular portion of patella in extensor mechanism tracking and strength wassuch a way that a longitudinal ridge of bone checked and was found satisfactory. Fig. 3. Intraoperative (A) and schematic diagram (B) showing securing of allograft proximally.
Management of Extensor Mechanism Deficit as a Consequence of Patellar Tendon Loss Malhotra et al 1149 Table 2. Follow-up, Range of Motion, and Knee Scores Follow-up Preoperative ROM Postoperative ROM Preoperative Knee Postoperative KneePatient (mo) (Degrees) (Degrees) Score Score1 30 40-90 0-100 21 882 24 45-100 10-90 18 763 14 40-110 0-100 27 684 16 30-100 0-90 22 84 ROM indicates range of motion.Postoperative Care and Rehabilitation patients had no extensor lag at their most recent follow-up. The mean knee score at the time of the In the operating room, the limb was placed in full latest follow-up was 79 points (range, 68 to 88extension in a plaster slab. The patients were given points). Radiographic analysis showed all allograftsa knee brace in extension after wound inspection at to be incorporated proximally as well as distally by3 days. Patients were maintained with the knee in 12 months.full extension for 8 weeks after surgery. During this The results are depicted in Table 2. Postoperativeperiod, we allowed touch-down weight-bearing range of motion and x-rays of 1 patient are shown inonly. Isometric static quadriceps contractions were Figs. 4 and 5.encouraged. At 6 weeks, patients were advanced At their recent follow-up, all but 1 patient wereto weight-bearing as tolerated. During weight- able to walk without an assistive device. One patientbearing, we locked the brace in full extension. At had a superficial wound infection, which was12 weeks, we allowed further active flexion up to a controlled by intravenous antibiotics. No othermaximum of 90°, and gentle quadriceps strength- complications were seen.ening exercises were initiated. Passive flexion wasnot permitted, to minimize the chance of graftfailure and early attenuation. Postoperative x-rays Discussionwere taken at each follow-up for the evaluation ofthe incorporation of allograft bone proximally as The extensor mechanism seems to play a crucialwell as distally. role in primary as well as revision total knee arthroplasty. The prevalence of complications Results related to the extensor mechanism in total knee arthroplasty is around 4% [2,9,10]. Patellar One patient had an associated valgus laxity of 15° maltracking; patella alta/baja; abnormal patellaras well as a 10° extensor lag. The valgus laxity was wear; patellar subluxation/dislocation; and disrup-treated with a medial collateral ligament reconstruc- tion of extensor mechanism caused by patellation using the semitendinosus. The remaining 3 fracture, quadriceps tendon rupture, and patellar Fig. 4. Postoperative active range of motion at 24 months.
1150 The Journal of Arthroplasty Vol. 23 No. 8 December 2008 appearance, weakness of ankle plantar flexion, and residual extensor lag . Augmentation with xenograft and synthetic carbon fiber implants is largely unsuccessful . Allograft reconstruction of the extensor mechan- ism has been debatable. Options for allograft reconstruction include patellar tendon alone , Achilles tendon allograft, Achilles tendon-calca- neum composite allograft , and extensor mechanism composite allograft [6,7]. Emerson, Jr, et al [6,7], had reported promising early results after use of an extensor mechanism allograft to reconstruct a failed extensor mechanism in patients with a previous total knee arthroplasty.Fig. 5. Postoperative x-rays showing good incorporation However, the authors concluded that the long-termof allograft proximally as well as distally. results needed further evaluation. The original technique of Emerson, Jr, et al, was modified by Nazarian and Booth, Jr , who tensioned thetendon rupture, constitute the spectrum of exten- allograft tightly after ensuring full knee extensionsor mechanism complications. before placement of the graft. Intraoperative under- Patellar tendon rupture is a devastating extensor tensioning of graft and poor graft–soft tissue healingmechanism complication after total knee arthroplasty. due to poor fibroblastic response, leading to severeIts incidence has been reported as ranging from 0.17% attenuation of graft host junction, particularly at theto 2.5% in various series [1,2]. Factors associated with proximal quadriceps junction, has remained apatellar tendon rupture include a difficult exposure in problem with these techniques [6-8].a stiff knee, extensive release of the patellar tendon at Our modification of this technique is based on thethe time of surgical exposure, manipulation for the rationale of replacing the incompetent tissue withtreatment of limited motion, revision total knee whole, structurally sound tissue, placing surgicalarthroplasty, and distal realignment of the extensor junctions at the most favorable healing sites possiblemechanism to treat patellar maltracking . To in the well-vascularized environment of proximalprevent intraoperative rupture, various measures tibial metaphysis and the host patellar cancellous(namely, lateral release/proximal release; tibial tuber- bone. This technique produces more favorablecle osteotomy; holding patellar tendon with clamp, healing, particularly at the proximal junction, bywasher, or pin) have been in vogue. Postoperatively providing a bony cancellous bed of the host bone foraggressive rehabilitation; falls with acute flexion; repair. Durability of the repair was evident from theremanipulation; and progressive attrition of extensor fact that the repair was holding even at the end ofmechanism due to prosthetic impingement, removal 30 months without any extension lag except in 1of too much bone from patella, or devascularization patient. This technique, however, is possible onlyby surgical process, have also been associated with because we do not routinely resurface the patella andpatellar tendon rupture. had a good host patellar bone stock. In case of poor The management of a chronically deficient patellar bone stock, we recommend the technique ofextensor mechanism depends upon availability Emerson, Jr, et al [6,7], wherein the extensorand quality of local tissues, functional demands mechanism is reconstructed by securing the allograftof the patient, and overall medical status, including with the host quadriceps tendon proximally.comorbidities. There is no role of conservative In summary, this technique may play a significantmanagement. Primary repair with wires, staples, or role in the outcome of reconstruction of a chronicsutures is often unsuccessful [1,12,13]. Augmenta- patellar tendon loss with an extensor mechanismtion of primary repair with autogenous tissuelike allograft after a total knee arthroplasty. Our methodfree fascia lata, plantaris tendon, gracilis tendon, of extensor mechanism reconstruction, which aimsand semitendinosus graft, has also been described, for bone-to-bone healing, is durable and has notbut results are consistently poor [1,13-15]. The use shown deterioration over time. We recommend thisof a medial gastrocnemius flap for reconstruction method for extensor mechanism reconstruction inhas the advantage of providing viable autogenous cases where host patellar bone stock is good. Carefultissue to cover the anterior-inferior aspect of the attention to graft preparation and handling, provid-knee but has the disadvantages of a poor cosmetic ing an environment for bone-to-bone healing both
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