Bone resection and ligament treatment for flexion contracture in knee arthroplasty

A retrospective study of 103 knees (88 patients) who had primary total knee arthroplasty with a flexion contracture ranging from 20 degrees to 60 degrees was done to tabulate the primary soft tissue structures released during surgery and to identify any residual deformity. The average flexion contracture preoperatively was 27.1 degrees +/- 8 degrees and postoperatively was 2.7 degrees +/- 3.4 degrees (range, 0 degrees -10 degrees ). The average followup was 70.4 months (range, 12-180 months). Only medial or lateral soft tissue balancing procedures were necessary to correct the flexion contracture in 37 knees (35.9%) and no medial or lateral release was necessary in 25 knees (24.3%), of which 16 had a balanced posterior cruciate ligament. The posterior capsule was released on the deformity side of the knee in 15 knees (14.6%) and on the opposite side of the deformity in seven knees (6.8%). The posterior cruciate ligament was balanced in 21 knees (20.4%) and was released in four knees (3.9%). For all knees in which the posterior cruciate ligament was released or balanced, it was done for excessive rollback and tightness in flexion and not for flexion contracture management. In two patients (2%) an additional 4 mm of distal femur was resected for a 45 degrees and a 25 degrees flexion contracture. The data suggest that a contracted collateral ligament is the most likely primary structure whose effective release allows correction of the flexion contracture in most cases.     

Stability after medial collateral ligament release in total knee arthroplasty.

Six knees from cadavers were tested for change in stability after release of the medial collateral ligament with posterior cruciate-retaining and substituting total knee replacements. Load deformation curves of the joint were recorded in full extension and 30 degrees, 60 degrees, and 90 degrees flexion under a 10 N-m varus and valgus torque, 1.5 N-m internal and external rotational torque, and a 35 N anterior and posterior force to test stability in each knee. The intact specimen and posterior cruciate ligament-retaining total joint replacement were tested for baseline comparisons. The superficial medial collateral ligament was released, followed by release of the posterior cruciate ligament. The knee then was converted to a posterior-stabilized implant. After medial collateral ligament release, valgus laxity was statistically significantly greater at 30 degrees, 60 degrees, and 90 degrees flexion after posterior cruciate ligament sacrifice than it was when the posterior cruciate ligament was retained. The posterior-stabilizing post added little to varus and valgus stability. Small, but significant, differences were seen in internal and external rotation before and after posterior cruciate ligament sacrifice. The posterior-stabilized total knee arthroplasty was even more rotationally constrained in full extension than the knee with intact medial collateral ligament and posterior cruciate ligament.     

TKA术中中度屈曲畸形骨与韧带的处理

目的探讨膝关节置换术中中度屈曲畸形骨与韧带的正确处理程序。方法对104例屈曲畸形在20～60°的初次置换患者进行回顾性研究,了解术中软组织松解步骤及每步松解后畸形残留情况。结果在随访36个月后屈曲畸形由术前平均32.4°恢复到术后3.4°。59例膝在内外软组织松解后屈曲畸形矫正;虽然所有患者均进行了不同程度的后关节囊松解,但只有39例是必需的;有6例需要额外的股骨远端截骨。结论充分的后关节囊及内外副韧带松解可以矫正绝大部分屈曲畸形,增加股骨远端截骨并非必须,后交叉韧带松解的原因是因为屈曲间隙紧张和增加股骨假体后方滚动。     

Effect of tibial slope or posterior cruciate ligament release on knee kinematics

An experimental study using fresh human cadaver knees was designed to evaluate the effect of partial posterior cruciate ligament release or posterior tibial slope on knee kinematics after total knee arthroplasty. Varus and valgus laxity, rotational laxity, anteroposterior laxity, femoral rollback, and maximum flexion angle were evaluated in a normal knee, an ideal total knee arthroplasty, and a total knee arthroplasty in which the ligaments were made to be too tight in flexion. The total knee arthroplasty specimens then were subjected to either partial posterior cruciate ligament release or increased posterior tibial slope, and the tests were repeated. Posterior tibial slope increased varus and valgus laxity, anteroposterior laxity, and rotational laxity in the knee that had flexion tightness. Posterior cruciate ligament release corrected only anteroposterior tightness, and had no effect on the abnormal collateral ligament tightness. Increased posterior tibial slope significantly improved varus and valgus laxity and rotational laxity in the knee that was tight in flexion more than with release of the posterior cruciate ligament. Therefore increasing posterior tibial slope is preferable for a knee that is tight in flexion during total knee arthroplasty.     

Total knee arthroplasty ligament balancing and gap kinematics with posterior cruciate ligament retention and sacrifice

This cadaver study was undertaken to gain insight into the effects that posterior cruciate ligament retention and sacrifice would have on the amount of deformity correction obtained with medial and lateral structure release during total knee arthroplasty. Twenty-seven cadaveric specimens were used to sequentially release medial and lateral structures with and without posterior cruciate support. Each release sequence was tested in full extension and 90 degrees flexion. In full extension, the resulting change into valgus after release of the posterior cruciate ligament, posteromedial capsule/oblique ligament complex, superficial medial collateral ligament, and pes anserinus and semimembranosus tendons was 6.9 degrees, and it increased to 13.4 degrees in 90 degrees flexion. With preservation of the posterior cruciate ligament this decreased to 5.2 degrees in extension and 8.7 degrees in flexion. Changes seen in 90 degrees flexion were significantly greater than those in full extension. For the valgus knee model with release of the posterior cruciate ligament, posterolateral capsule, lateral collateral ligament, iliotibial band, popliteus tendon, and lateral head of the gastrocnemius, 8.9 degrees of change into varus was seen in extension and 18.1 degrees in 90 degrees flexion. With posterior cruciate ligament retention 5.4 degrees and 4.9 degrees of change into varus was seen in extension and flexion, respectively. Significantly less change with retention of the posterior cruciate ligament was seen with both medial and lateral release and more opening of the flexion gap was seen on the release side of the joint for all groups except those with lateral release with sacrifice of the posterior cruciate ligament.     

Effects of joint load on the stiffness and laxity of ligament-deficient knees. An in vitro study of the anterior cruciate and medial collateral ligaments

We measured the effects of serial section of the medial collateral ligament and anterior cruciate ligament and of the anterior cruciate ligament and medial collateral ligament on anterior-posterior force-versus-displacement and tibial torque-versus-rotation response curves for seven fresh frozen cadaver knees at zero and 20 degrees of flexion before and after application of as much as 925 newtons of compressive load on the tibiofemoral joint. Section of the anterior cruciate ligament always increased anterior laxity in an unloaded specimen; joint load reduced this increase by a greater amount at zero degrees than at 20 degrees of flexion. Joint load was more effective in limiting anterior laxity in anterior cruciate-deficient specimens at low levels of applied anterior force; at higher levels of applied force, the effects of joint congruency were overcome and ligament restraints came into play. Section of the medial collateral ligament increased anterior laxity in an unloaded knee only for specimens in which the anterior cruciate ligament had been previously sectioned; joint load eliminated this increase at full extension but did not do so at 20 degrees of flexion. The medial collateral ligament was the more important of the two ligaments in controlling torsional laxity. Secondary section of either ligament (the other ligament having been sectioned first) produced a greater increase in laxity than did primary section of that ligament in an intact knee. Increases in torsional laxity due to primary section of either ligament were unaffected by the application of joint load. Joint load reduced increases in laxity that were due to secondary section of the medial collateral ligament.     

Quantification of effect of sequential posteromedial release on flexion and extension gaps: a computer-assisted study in cadaveric knees

A novel sequence of posteromedial release consistent with surgical technique of total knee arthroplasty was performed in 15 cadaveric knees. Medial and lateral flexion and extension gaps were measured after each step of the release using a computed tomography-free computer navigation system. A spring-loaded distractor and a manual distractor were used to distract the joint. Posterior cruciate ligament release increased flexion more than extension gap; deep medial collateral ligament release had a negligible effect; semimembranosus release increased the flexion gap medially; reduction osteotomy increased medial flexion and extension gaps; superficial medial collateral ligament release increased medial joint gap more in flexion and caused severe instability. This sequence of release led to incremental and differential effects on flexion-extension gaps and has implications in correcting varus deformity.     

Medical restraints to anterior-posterior motion of the knee

We investigated the motion of cadaver knees before and after section of the medial structures and anterior cruciate ligament. The knees were tested using a 5-degrees-of-freedom in vitro knee-testing apparatus that measured anterior-posterior, medial-lateral, and axial displacement as well as internal-external and valgus-varus rotation. The flexion angle could be varied but was fixed for each individual test. A 125-newton anterior-posterior force was applied perpendicular to the tibial shaft and the resulting motion of the knee was measured. In five knees the anterior cruciate ligament was cut first, followed by progressive cuts of the structures on the medial side (superficial medial collateral ligament, deep medial ligament, oblique fibers of the superficial medial ligament, and the posteromedial part of the capsule). Conversely, in five knees the medial structures were progressively cut first, followed by section of the anterior cruciate ligament. Tests were performed after each cut. With an intact anterior cruciate ligament, progressive cutting of the medial side had no effect on anterior and posterior displacements. When section of the medial structures followed cutting of the anterior cruciate ligament, anterior displacement exceeded that seen after isolated section of the anterior cruciate ligament. The anterior and posterior load-tests were repeated with the tibia fixed in 5 degrees of internal and 5 degrees of external rotation. Fixed external rotation had no effect on anterior and posterior displacements. Fixed internal rotation significantly decreased anterior displacement only when both the anterior cruciate ligament and the medial structures were cut.(ABSTRACT TRUNCATED AT 250 WORDS)     

Two-stage reconstruction with autografts for knee dislocations

Traumatic knee dislocations are severe injuries that involve damage to the anterior cruciate ligament, the posterior cruciate ligament, and the lateral or medial ligamentous structures. There are no established methods of treatment. The objective of the current study was to report the clinical outcome of a two-stage autologous reconstruction on nine knees (eight patients). The mean followup was 40.1 months. The first stage of the reconstruction was done at a mean of 2 weeks after the injury, and the posterior cruciate ligament was reconstructed by an arthroscopically assisted technique using contralateral autogenous hamstring tendon as the graft material. Three months later, the second stage of the reconstruction was done for the ligaments that had not healed with conservative treatment. Arthroscopically assisted anterior cruciate ligament reconstruction was done on all of the knees using the ipsilateral autogenous hamstring tendon or bone-patellar tendon-bone as the graft material. At the same time, a medial collateral ligament reconstruction using an autogenous semitendinosus tendon was done on one knee, and reconstruction of the posterolateral ligamentous structures using a biceps tendon was done on three knees. Each of the knees that was reconstructed was capable of full extension, and the mean degree of passive flexion was 139.5 degrees +/- 5.2 degrees. The mean side-to-side difference in anteroposterior total laxity (KT-1000 arthrometer, manual maximum) was 2.3 +/- 1.9 mm. None of the knees had lateral or medial instability. All of the injured ligaments were able to be reconstructed with autografts, and severe contracture was able to be prevented. A good clinical outcome can be achieved when two-stage reconstruction is used for traumatic knee dislocations.     

Stress radiography in acute ligamentous injuries of the knee

Stress radiography was performed on 60 acute ligamentous injuries of the knee under general anaesthesia using a simple standard technique. Laxity on angular stress in extension was evident when the posterior cruciate ligament was torn in association with a collateral capsular tear. The same test repeated in 20–30 ° of flexion was abnormal when the collateral capsule alone was torn and the laxity always exceeded 5 °. Where both cruciate ligaments were torn the laxity exceeded 10 °. Lateral stress radiographs in the presence of an isolated capsular tear demonstrated rotatory laxity with a glide rarely exceeding 10 mm. The addition of a torn anterior cruciate ligament resulted in sagittal laxity greater than 7 mm and a tear of the posterior cruciate ligament, irrespective of the associated pathology, resulted in a laxity exceeding 12 mm.     

The effect of section of the medial collateral ligament on force generated in the anterior cruciate ligament

Ten fresh-frozen knees from cadavera were instrumented with a specially designed transducer that measures the force that the anterior cruciate ligament exerts on its tibial attachment. Specimens were subjected to tibial torque, anterior tibial force, and varus-valgus bending moment at selected angles of flexion of the knee ranging from 0 to 45 degrees. Section of the medial collateral ligament did not change the force generated in the anterior cruciate ligament by applied varus moment. When valgus moment was applied to the knee, force increased dramatically after section of the medial collateral ligament; the increases were greatest at 45 degrees of flexion. Section of the medial collateral ligament had variable effects on the force generated in the anterior cruciate ligament during internal rotation but dramatically increased that generated during external rotation; these increases were greatest at 45 degrees. Section of the medial collateral ligament increased mean total torsional laxity by 13 degrees (at 0 degrees of flexion) to 20 degrees (at 45 degrees of flexion). Application of an anteriorly directed force to the tibia of an intact knee increased the force generated in the anterior cruciate ligament; this increase was maximum near the mid-part of the range of tibial rotation and minimum with external rotation of the tibia. Section of the medial collateral ligament did not change the force generated in the anterior cruciate ligament by straight anterior tibial pull near the mid-part of the range of tibial rotation.(ABSTRACT TRUNCATED AT 250 WORDS)     

The medial approach for operative release of post-traumatic contracture of the elbow

We treated post-traumatic contracture of the elbow in 13 consecutive patients (14 elbows) by operative release. Through a single medial approach, the posterior oblique bundle of the medial collateral ligament was resected, followed by posterior and anterior capsulectomies. An additional lateral release through a separate incision was required in only four elbows. The results were assessed at a mean interval of 57 months after operation. Before surgery active extension lacked 43 degrees which improved to 17 degrees after operation. Active flexion before operation was 89 degrees, which improved to 127 degrees. The mean arc of movement increased from 46 degrees to 110 degrees. All 14 elbows showed scarring of the posterior oblique bundle of the medial collateral ligament. Neither the interval from injury to operative release nor the age of the patient affected the results. A medial approach is useful to reveal and excise the pathological changes in the medial collateral ligament. It is a safe and effective route through which to correct post-traumatic contracture of the elbow.     

Soft tissue release in total knee arthroplasty. Cadaver study using knees without deformities

Soft tissue releases are performed to correct fixed deformities in total knee arthroplasty. The goal of this in vitro study was to investigate the relationship between the individual steps in a medial (eight anatomic specimen knees) or lateral (four anatomic specimen knees) soft tissue release sequence, the resulting change in the medial and lateral tibiofemoral gaps, and the change in coronal angulation caused by 10 Nm varus and valgus moments in extension and 90 degrees flexion. An optical encoder was used to measure the coronal angulation. The tibiofemoral gaps were measured with calipers with the knee distracted by a 53-N load. In the medial release sequence, a significant increase in coronal angulation and medial gap occurred after the release of the anteromedial sleeve 8 cm from the medial joint line. In the lateral release sequence, there was a significant increase in the coronal angle and lateral gap after the lateral collateral ligament and popliteus tendon were released from the femur. Release of the posterior cruciate ligament led to a significant increase in angle and gap in medial and lateral release sequences. These results are specific for the particular release sequences studied, with release of the posterior cruciate being the final step in each sequence.     

严重屈膝畸形的人工膝关节表面置换术

为探讨重度屈膝畸形（屈曲角度≥６０度）如何进行人工全膝关节表面置换术（ＴＫＲ）,作者于１９８７年４月～１９９４年５月对２３例患者、３７个膝关节行ＴＫＲ,均获得了较好的临床治疗效果。术后患者疼痛明显减轻,屈曲角度由术前的平均７７．９７度降至术后的平均６．７度,其中６２．１％膝关节屈曲角度＜５度,关节屈伸活动度也由术前的平均２５．６度增至术后的平均８３．６度。膝评分优良者占７３．８３％,膝功能评分优良者占１３％。作者认为,重度屈膝畸形并非ＴＫＲ的绝对禁忌证,关键在于术中对后关节囊、侧副韧带等挛缩组织的彻底松解和平衡,必要时应切除后交叉韧带并适当多切除股骨髁及胫骨平台骨质。     

Primary total knee arthroplasty in the valgus knee: creating a balanced soft tissue envelope

Lateral tissue releases in valgus total knee arthroplasty frequently produce asymmetric flexion-extension gaps and ligamentous instability. This study compared 2 lateral-release sequences and quantified the effects of sequential lateral capsular ligamentous structure release. One knee from 7 paired specimens was released according to a 4-step sequence: posterior cruciate ligament (PCL), ibiotibial tract (IT band), popliteus tendon/lateral collateral ligament (PT/LCL), and biceps femoris tendon. The contralateral knees were released according to a 5-step sequence: PCL, posterolateral capsule, IT band, PT, and LCL. After each release step, flexion and extension gaps were measured and recorded for the medial and lateral aspects. The 5-step sequence produced more symmetric flexion-extension gaps, whereas the absolute magnitudes of correction were lower than with the 4-step sequence. LCL sacrifice in both sequences produced marked lateral flexion-extension gap asymmetry.     

Reconstruction of knees with combined cruciate deficiencies: a biomechanical study

BACKGROUND: Clinical results of dual cruciate-ligament reconstructions are often poor, with a failure to restore normal anterior-posterior laxity. This could be the result of improper graft tensioning at the time of surgery and stretch-out of one or both grafts from excessive tissue forces. The purpose of this study was to measure anterior-posterior laxities and graft forces in knees before and after reconstructions of both cruciate ligaments performed with a specific graft-tensioning protocol. METHODS: Eleven fresh-frozen cadaveric knee specimens underwent anterior-posterior laxity testing and installation of load cells to record forces in the native cruciate ligaments as the knees were passively extended from 120 degrees to -5 degrees with no applied tibial force, with 100 N of applied anterior and posterior tibial force, and with 5 N-m of applied internal and external tibial torque. Both cruciate ligaments were reconstructed with a bone-patellar tendon-bone allograft. Only isolated cruciate deficiencies were studied. We determined the nominal levels of anterior and posterior cruciate graft tension that restored anterior-posterior laxities to within 2 mm of those of the intact knee and restored anterior cruciate graft forces to within 20 N of those of the native anterior cruciate ligament during passive knee extension. Both grafts were tensioned at 30 degrees of knee flexion, with the posterior cruciate ligament tensioned first. Measurements of anterior-posterior knee laxity and graft forces were repeated with both grafts at their nominal tension levels and with one graft fixed at its nominal tension level and the opposing graft tensioned to 40 N above its nominal level. RESULTS: The anterior and posterior cruciate graft tensions were found to be interrelated; applying tension to one graft changed the tension of the other (fixed) graft and displaced the tibia relative to the femur. The posterior cruciate graft had to be tensioned first to consistently achieve the nominal combination of mean graft forces at 30 degrees of flexion. At these levels, mean forces in the anterior cruciate graft were restored to those of the intact anterior cruciate ligament under nearly all test conditions. However, the mean posterior cruciate graft forces were significantly higher than the intact posterior cruciate ligament forces at full extension under all test conditions. Anterior-posterior laxity was restored between 0 degrees and 90 degrees of flexion with both grafts at their nominal force levels. Overtensioning of the anterior cruciate graft by 40 N significantly increased its mean force levels during passive knee extension between 110 degrees and -5 degrees of flexion, but it did not significantly change anterior-posterior laxity between 0 degrees and 90 degrees of flexion. In contrast, overtensioning of the posterior cruciate graft by 40 N significantly increased posterior cruciate graft forces during passive knee extension at flexion angles of <5 degrees and >95 degrees and significantly decreased anterior-posterior laxities at all flexion angles except full extension. CONCLUSIONS: It was not possible to find levels of graft tension that restored anterior-posterior laxities at all flexion positions and restored forces in both grafts to those of their native cruciate counterparts during passive motion. Our graft-tensioning protocol represented a compromise between these competing objectives. This protocol aimed to restore anterior-posterior laxities and anterior cruciate graft forces to normal levels. The major shortcoming of this tensioning protocol was the dramatically higher posterior cruciate graft forces produced near full extension under all test conditions.     

A biomechanical evaluation of the Lenox Hill knee brace

This study was conducted to determine the effectiveness of the Lenox Hill knee brace in limiting anterior translation and external rotation of the tibia in reference to the femur in normal and ligament-deficient knees. Four fresh cadaver knees were fitted with Lenox Hill knee braces according to the manufacturer's guidelines. A computer-assisted testing apparatus was constructed that allowed each knee to be tested as a function of knee flexion angle, joint load, and soft tissue integrity. Each knee served as its own control. While 45 kg of anterior force was applied to the tibia of the anterior cruciate ligament deficient knees, the Lenox Hill knee brace was able to decrease anterior translation from an average of 10 mm, to 5.7 mm, at 30 degrees of flexion when no vertical load was present. This limiting effect was lost when the medial collateral ligament was sectioned in addition to the anterior cruciate ligament or when both the medial and the lateral collateral ligaments were sectioned along with the anterior cruciate ligament. When 20 Newton-meters (Nm) of torque was applied to the femurs at 30 degrees of flexion without vertical load, the Lenox Hill knee brace limited external rotation of the tibia in all tested categories. For intact knees at 30 degrees of flexion and no vertical load, the Lenox Hill knee brace decreased external rotation from 18 degrees to 10 degrees. In the anterior cruciate ligament-sectioned knees, external rotation was decreased from an average of 20.2 degrees to 16.1 degrees. In the knees with sectioned anterior cruciate and medial collateral ligaments, the average reduction was from 21.2 degrees to 15.4 degrees.(ABSTRACT TRUNCATED AT 250 WORDS)     

Surgical procedure for flexion contracture and recurvatum in total knee arthroplasty

A specific protocol for dealing with flexion contracture and recurvatum in total knee arthroplasty surgery was evaluated. In cases of flexion contracture, this protocol included choosing the larger femoral size when the femur was between sizes to make the flexion space smaller and to allow overresection of the tibial surface to correct the flexion contracture. In all cases, bone resection was done first, osteophytes were resected next, and ligaments were balanced after the trials were in place. Extra bone was resected from the distal femur to correct residual flexion contracture only if ligament balancing failed to correct the deformity. In cases of recurvatum, the smaller femoral size was chosen to enlarge the flexion space, allowing underresection of the tibia to stabilize the knee in extension. The cutting guides were positioned so that 3 to 5 mm less than the distal thickness of the femoral component was removed to stabilize the knee in extension. To evaluate this protocol, a computerized database was used to review records of 530 patients (552 knees) who had flexion contracture (542 knees) or recurvatum (10 knees) before surgery. Ligament release and correction of varus or valgus contracture corrected flexion contracture to less than 3 degrees in 515 knees (95%). Sixteen knees (3%) had release of the posterior capsule to correct residual flexion contracture, and 11 knees (2%) required overresection of the distal femoral surface to achieve correction of flexion contracture. By 1 year the flexion contracture was 2 degrees +/- 1 degree. In the knees with preoperative recurvatum, none had residual recurvatum at the conclusion of surgery, and none had recurrent deformity. None of the knees required a hinge or a stabilized component with a highly conforming central post.     

Gap configuration and anteroposterior leg axis after sequential medial ligament release in rotating-platform total knee arthroplasty

BACKGROUND: Soft tissue management is a major issue in total knee replacement. There have been very few papers dealing with its effect on leg axis and tibiofemoral gap. METHODS: In a cadaver specimen study, we analyzed this effect by performing a sequential medial soft tissue release after a mobile-bearing total knee arthroplasty. Measurements were obtained using a CT-free navigation system (Ci navigation system). RESULTS: We found the highest increase in leg axis and medial gap when releasing the anteromedial tibial sleeve of the capsule 6 cm below the joint line, in extension, and after dividing the medial collateral ligament, in flexion, when releasing the medial half of the posterior cruciate ligament. There were differences in amount of change between extension and flexion, especially when releasing the medial half of the posterior cruciate ligament. In extension, the lateral gap remained the same as in flexion. INTERPRETATION: Implementation of computer-assisted surgery has allowed this first navigation-controlled study investigating the effect of soft tissue release in TKR with rotating platform. Each sequential release step has the desired effect on a.p. leg axis and tibiofemoral gaps. It is important that the differences between the effects in extension and flexion be noted.     

Selective ligament release in total knee arthroplasty of the knee in valgus.

An approach to the valgus knee based on anatomic function of ligaments in flexion and extension consistently yields a knee that is balanced in flexion and extension when the implants have been positioned correctly. Two hundred thirty-one knees had a valgus deformity (range, 12 degrees-45 degrees) and were corrected with valgus alignment to 5 degrees by resecting the intact joint surfaces to match implant thickness. Femoral joint surfaces were aligned in 5 degrees valgus to the long axis of the femur and parallel to the epicondylar axis of the femur in flexion and extension. The tibial surfaces were aligned perpendicular to the long axis of the tibia. For knees that were tight in flexion and extension, the lateral collateral ligament and popliteus tendon were released. Those knees that remained tight only in extension had release of the iliotibial band. Posterior capsular release was done only when necessary for persistent lateral ligament tightness. Neither ligament advancement procedures nor varus or valgus stabilized implant systems were needed to achieve stability with this procedure. The knees with ligament releases all fell within a range of 4 degrees to 7 degrees mean varus and valgus laxity, and were not significantly different from one another. No cases of clinical instability occurred, and joint stability did not deteriorate with time.