Biomechanical Analysis of Internal Bracing for Treatment of Medial Knee Injuries

n Feature Article Biomechanical Analysis of Internal Bracing for Treatment of Medial Knee Injuries BRIAN B. GILMER, MD; TIMOTHY CRALL, MD; JEFFREY DELONG, BS; TAKANORI KUBO, MD; GORDON MACKAY, MD; SUNIL S. JANI, MD, MS ing of surgical intervention remain con- abstract troversial, and postoperative stiffness is The internal brace technique uses a high-strength suture tie to augment injured tissues or a primary repair, allowing early rehabilitation. Anatomic repair with The authors are from the Department of Or- internal bracing is a novel and promising treatment for femoral-sided medial thopedics and Sports Medicine (BBG, TC), Mam- knee avulsion injuries of the medial collateral ligament and posterior oblique moth Orthopedic Institute, Mammoth Lakes, ligament. Unfortunately, biomechanical and clinical data are lacking. To evalu- California; the College of Medicine, Medical Uni- ate this technique compared with other treatment options, 3 assays of 9 ca- versity of South Carolina (JD), Charleston, South Carolina; AR-Ex Medical Group (TK), Tokyo, Ja- daveric matched pairs (54 knees) were tested to failure at 30° under valgus pan; the Mackay Clinic (GM), Stirling, Scotland; load in a biomechanical testing apparatus. The primary outcome measure was and the Taos Orthopaedic Institute (SSJ), Taos, moment at failure (Nm), with secondary outcome measures of stiffness (Nm/°), New Mexico. valgus angulation at 10 Nm (°), and valgus angulation at failure (°). Repair with Mr DeLong and Dr Kubo have no relevant fi- nancial relationships to disclose. Dr Gilmer has internal bracing was compared with the intact state, repair alone, and allograft received nonfinancial support from Arthrex and reconstruction. The mean moment to failure (62.5±24.9 Nm) for internal brac- other support from Arthrex, Smith & Nephew, ing was significantly lower than that for intact specimens (107.2±39.7 Nm) Breg, Donjoy, Stryker, Tornier, and U&I. Dr Crall (P=.009). Mean moment to failure and valgus angle at failure were significant- has received support from Arthrex and Smith & Nephew. Dr Mackay is a paid consultant for and ly greater for internal bracing (95±31.9 Nm) than for repair (73.4±27.6 Nm) receives royalties from Arthrex. Dr Jani has re- (P=.05). Internal bracing was similar to reconstruction for the primary outcome ceived nonfinancial support from Arthrex and oth- measure (53.5±26.3 Nm vs 66.9±28.8 Nm) (P=.227) and for all secondary out- er support from Arthrex, Smith & Nephew, Breg, come measures. These findings indicate that posteromedial knee repair with Donjoy, Stryker, Tornier, and U&I. The authors thank Dolores Guerrero, MS, for internal bracing for femoral-sided avulsions is superior to repair alone and is assistance with statistical analysis and manu- similar to allograft reconstruction for all parameters measured; however, this script preparation, and John Konicek, BS, for as- technique did not re-create biomechanical properties equivalent to the intact sistance with biomechanical testing and statistical state. [Orthopedics. 2016; 39(3):e532-e537.] analysis. Correspondence should be addressed to: Brian B. Gilmer, MD, Department of Orthopedics and Sports Medicine, Mammoth Orthopedic Insti- edial-sided ligamentous knee treatment.1,2 However, severe (grade 3) or tute, PO Box 660, 85 Sierra Park Rd, Mammoth injuries are common, and combined (multiligament) injuries may Lakes, CA 93546 ([email protected]). Received: June 25, 2015; Accepted: Novem- Mthe majority of medial-sided require surgical intervention to stabilize ber 24, 2015 ligament injuries heal with nonoperative the joint.3-7 Treatment technique and tim- doi: 10.3928/01477447-20160427-13 e532 COPYRIGHT © SLACK INCORPORATED n Feature Article the most common complication.6-8 Ana- tomic reconstruction of the superficial and deep portions of the medial collateral ligament (MCL) and the posterior oblique ligament (POL) using soft tissue grafts, bone sockets, and interference screw fixation has been shown to result in nearly normal knee stability without biomechanical overconstraint and may be considered the gold standard.9 However, anatomic reconstruction autografts have associated morbidity, and allografts have risks.10-12 Therefore, the goal of any op- erative technique for injuries to the posteromedial knee is to restore anatomy and stability, minimize patient morbidity and risk, and allow for immediate range of motion to prevent postoperative stiffness. An alternative surgical technique for Figure 2: Photograph showing a left knee mounted severe and combined medial knee injuries in the testing apparatus in an anteromedial view (rotated 90° left to orient the femur above and the is posteromedial corner reconstruction us- tibia below). The white plastic ruler delineates the ing a technique combining repair13-15 with patella (right) from the medial side (left), where internal bracing.16 The purpose of this the femoral condyle and joint line are marked hori- study was to compare posteromedial ana- zontally in ink, and the medial collateral ligament is marked with ink above and below the femoral tomic repair with internal bracing to the condyle and joint lines. intact state, to anatomic repair alone,13-15 and to anatomic allograft reconstruction.9 The hypothesis for the study was that the Figure 1: Photograph showing a left knee speci- long axis of the femur positioned perpen- biomechanical properties of anatomic re- men with the medial collateral ligament (M), dicular to the direction of the applied val- pair with internal bracing would be supe- posterior oblique ligament (P), and semimembra- gus load to prevent internal and external rior to repair alone and similar to recon- nosus tendinous insertion on the posteromedial rotation. The proximal end of the femur proximal tibia (*) identified. The dotted blue ink struction and the intact state. line (above M) represents the medial joint line, and the distal ends of the tibia and fibula and the horizontal dash (below M) represents the were potted in fiberglass resin. A valgus MATERIALS AND METHODS distal attachment of the superficial medial collat- preload of 5 N was applied to the potted Twenty-seven matched pairs of ca- eral ligament 6 cm distal to the joint line. portion of the tibia followed by loading at daver knees were used in the study and 20 mm/minute until failure (Figure 2). divided into 3 assays of 9 pairs per assay. for testing. In all of the knees, superficial The mode of failure was recorded. Assay 1 compared repair with internal soft tissue was dissected, and particular Failure was defined as the point at which bracing with the intact state, assay 2 com- care was taken to identify the entire MCL a change in displacement no longer ex- pared repair alone with repair with inter- and POL, the femoral medial epicondyle hibited concomitant force increases.17 nal bracing, and assay 3 compared ana- and adductor tubercle, and tibial insertion Moment, stiffness, and valgus displace- tomic repair with internal bracing with of the semimembranosus (Figure 1). ment angle at 10 Nm and at failure were allograft reconstruction. For each speci- recorded using Instron Systems software men donor number (to ensure matched Testing Protocol (WaveMaker, version 7.1). Moment is a pairs) side, age, and sex were recorded. Specimens were mounted on an In- measure of force over a given distance stron 8871 Electromechanical Dynamic (Nm). Moment was used to standard- Specimen Preparation Testing System (Instron, Norwood, Mas- ize force measurements about the knee Twenty-seven cadaveric fresh-frozen sachusetts) with a 5-kN load cell secured because of differences between cadaver knee matched pairs with no evidence of to the cross-head. The specimens were specimens. Differences in tibia length previous injury or disease were identified positioned at 30° of knee flexion with the and the bone cuts for each specimen re- MAY/JUNE 2016 | Volume 39 • Number 3 e533 n Feature Article Figure 3: Photograph showing dissection of a left knee. In this medial view, the medial collateral liga- Figure 4: Photograph showing repair of the pos- ment (right) and posterior oblique ligament (left) teromedial corner of a left knee. In this medial can be seen after scalpel release from the femur. view, the medial collateral ligament (distal blue ink) and anteromedial joint line (blue dots to right) are marked. The medial collateral ligament (upper sulted in loads being generated at differ- right) and posterior oblique ligament (upper left) ent distances from the joint. Therefore, are anatomically repaired to the femur. Suture Figure 5: Photograph showing the repair of a the moment arm (cm) was measured for anchors loaded with high-strength suture at the left knee in concert with structural internal brac- anatomic medial collateral ligament and posterior every sample and was multiplied to the ing of the posteromedial corner. This medial view oblique ligament femoral footprints secure the liga- shows anatomic repair of the medial collateral maximum load (N) to provide the moment. The repair is secured at 30° of knee flexion ligament(upper right) and posterior oblique ligament (Nm) about the joint. Stiffness is a for the medial collateral ligament and at full exten- ment (upper left) to the femur with structural ties. measure of the extent to which a material sion for the posterior oblique ligament, with varus Repair of the posteromedial corner in concert with stress. resists deformation in response to an ap- structural ties is secured at 30° of knee flexion for the medial collateral ligament and full extension for plied force. Constructs with a greater stiff- the posterior oblique ligament, with varus stress. ness demonstrate less deformity under a of 20 mm using a 4.5-mm diameter bit. given force. For the purpose of this study, A drill with stop was used to standardize the force represented by moment (Nm) the depth of drilling and depth of anchor stat) measuring 2 mm was placed under was divided by the change in angulation insertion.

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