Complete or partial disruption of the collateral ligament during total knee arthroplasty in severe deformities is a devastating complication which sometimes remains unnoticed at the time of surgery. We analysed 280 knees in 150 patients with over 30° varus with flexion (196 knees), flexion deformity alone (60 knees) & valgus deformity (24 knees) treated with primary total knee arthroplasty from January 2002 to January 2008. The mean age of patient was 65 years (ranging from 54 years to 78 years).

Problems encountered were avulsion of MCL from tibial attachment in 26 knees, femoral attachment avulsion with a bony fragment in 9 knees. Lateral collateral ligament was injured in 5 knees. In 12 knees with varus of >30° with element of tibial rotation medial release alone was not enough to balance the joint. Lateral collateral ligament tightening was needed in these cases using lateral epicondylar osteotomy. In 4 cases the medial collateral ligament was reconstructed using semi-tendinosus graft. Direct repair was not done in any case. Constrained knee prosthesis was used in only 22 knees to provide added stability. The mean duration of follow-up was 42 months. Stability of the knee was assessed clinically and on fluoro-radiography in full extension, 30°flexion and at 90° flexion of the knee. Seventy three percent (38/52) patients regained stability within 2 mm, 25% (13/52) had instability upto 4 mm and only one patient had gross instability needing hinge knee prosthesis. On the side of ligament reconstruction the ROM remained 10 to 15° less than the opposite side. Range of motion knee-brace was needed for 3 weeks in all cases. In cases with ligament reconstruction using Hamstring tendon, brace was used up to 12 weeks.

In conclusion identification of ligamentous insufficiency and its management will not only prevent unstable joint but also minimize the risk of revision in future. Lateral collateral ligament tightening is needed in certain select extreme varus deformities in addition to medial release.

INTRODUCTION:

Management of developmental dysplasia of hip in adult is challenging and needs more to be understood in terms of ideal implant, position of acetabulum and operative technique. Patient may present very late, usually when osteoarthritic changes develop followed by pain. Operative management is difficult because of hypoplastic femoral medullary canal and shallow acetabulum filled with soft tissues. Altered anatomy of neurovascular structures also pose a risk of being injured during surgery.

Post total knee arthroplasty, mid flexion instability can be described as a stable knee in full extension but as soon as knee starts bending instability is noticed and the knee becomes stable again at 90° of flexion. Mid flexion instability should not be confused with the true flexion instability. Such instability may be not be recognized in most cases because of subtleness of the nature of complaints of the patient. Soft tissue tension should be equal not only medio-laterally but also in antero-posterior alignment. The knee needs to be balanced in the complete arc of motion. To understand this it should be remembered that main stabilizer of the knee in extension is the posterior capsule and in flexion are the collateral ligaments.

Main factors contributing to Mid Flexion instability are:

1.

Over release of anterior part of Medial Collateral Ligament (which is a stabilizer from 30° to 60° of motion).

In a fixed flexion deformity, suitable posterior release should be matched with the collateral frame before taking extra-distal femoral cuts. Every 2 mm of additional distal femoral cut causes mid flexion instability of 2 to 3° as was seen in a cadaveric study. It is important to understand the interplay between posterior structures and collateral structures. Normally collateral structures have some laxity at 5° flexion but at 0° knees are locked mainly because of the tension of the posterior structures.

We have classified mid flexion instability in three types:

Type I: Over-released MCL and Normalised Posterior capsule

Type II: MCL Normal, but Posterior capsule is tight / insufficiently released and to balance this disparity distal femur cut is increased.

Type III: A Combination of above two conditions with MCL and Postero-medial Capsule both having laxity e.g. in a FFD with varus

It is a retro-prospective study. 411 patients with 600 knees were subjected to the study to assess mid-flexion instability in patients with primary Total Knee Arthroplasty. Follow was over a period of 5 years. Of the 600 TKA 60 were LCS prosthesis, 90 were PFC RP, 200 were PFC sigma and rest 250 were Stryker Scorpio. All patients were assessed by clinical and radiological evaluation. X-rays were taken in 0°, 30°, 60°. Arthrograms were also done to assess alignment of the joints. Fluroscopic studies were done in select few cases. Knee society score was noted for each patient and compared with pre-operative data.

Mid Flexion instability in a newer concept, the causes of which and further management protocols needs to be worked out. Mid Flexion instability is a failure to release the tight posterior capsule in a fixed flexion deformity. Over release of anterior MCL will result in mid flexion instability but in this situation knee may be unstable even at 90°.

There is still want of evidence in the current literature of any significant improvement in clinical outcome when comparing computer-assisted total knee arthroplasty (CA-TKA) with conventional implantation. Analysis of alignment and of component orientation have shown both significant and non-significant differences between the two methods. Not much work has been reported on clinical evidence of stability of the joint.

We compared computer-assisted and conventional surgery for TKA at 5.4 years follow-up for patients with varus osteoarthritic knees with deformity of more than 15∗. Our goal was to assess clinical outcome, stability and restoration of normal limb alignment.

We used CT and Cine video X ray techniques to analysize our results in Computer navigated and conventional TKRs. A three dimentional CT scan of the whole extremity was performed and evaluation was done in three planes; saggital, coronal and transverse views. CT scan was done between 10 to 14 days postoperative. Mean deviations in the mechanical axis, femoral and tibial plateau angles, and in transverse view, the trans-epicondylar axis vs posterior condylar axis were measured. The prospective randomized study comprised of 98 patients with surgery done on knees, one side navigated and other side conventional. Mean deviation in the mechanical axis was 2.2∗ in conventional knees and 1.8∗ in navigated knees. In 5 % of cases retinacular release was needed and CT analysis showed TEA in deviation of more than 2 ∗ in these cases. We analysed intraoperative data (surgical time and intraoperative complications), postoperative complications, lower limb alignment, radiographic complication on X-ray imaging, and clinical outcome throughknee and function score, range of motion and joint stability.

Our results showed that CAS had greater consistency and accuracy in implant placement and stability of joint in full extension and 90∗ flexion. In the coronal view, 93.3% in the CAS group had better outcomes compared with EM (73.4%). In the sagittal axis, 90.0% CAS also had better outcomes compared with EM (63.3%). Computer-navigated total knee arthroplasty helps increase accuracy and reduce “outliers” for implant placement.

Fixed flexion deformity is common in neglected cases of advanced arthritis of the knee.

The need and means of complete correction of fixed flexion deformity remains controversial. We analysed 60 patients of advanced arthritis with severe flexion deformity > 300 who underwent total knee arthroplasty between January 2002 to January 2008. The age ranged from 54 to 78 years (mean age of 62 years). All surgeries were performed using posterior cruciate substituting implant. Patients were followed for an average period of 42 months.

All patients were operated in a single stage. Distal femoral over-resection was done in addition to posterior, postero-medial and postero-lateral release. Posterior release was done upto the linea aspera. In 2 cases posterior capsular was released directly. A criteria was developed for sequential release on the basis of degree of flexion deformity.

Flexion deformity was fully corrected in 48 cases where as 50 of residual flexion remained in 5 cases with preoperative deformity of 40–600 and 100 residual flexion remained in 6 cases with preoperative deformity > 600. One patient with pre op fixed flexion deformity of 90* had to be treated with arthrodesis.

Our experience suggest that predetermined routine femoral over-resection in moderate to severe flexion deformity prior to balancing knee is not fraught with complications if our criteria are followed. Additional bony cuts (over-resection) and posterior soft tissue release is complementary to each other in correction of flexion deformity and it should be a sequential release. This technique saves time, reduces intraoperative difficulties and helps to correct flexion deformity maximally.