Does a mobile-bearing, high-flexion design increase knee flexion after total knee replacement?

This prospective randomised controlled double-blind trial compared two types of PFC Sigma total knee replacement (TKR), differing in three design features aimed at improving flexion. The outcome of a standard fixed-bearing posterior cruciate ligament-preserving design (FB-S) was compared with that of a high-flexion rotating-platform posterior-stabilised design (RP-F) at one year after TKR. The study group of 77 patients with osteoarthritis of the knee comprised 37 men and 40 women, with a mean age of 69 years (44.9 to 84.9). The patients were randomly allocated either to the FB-S or the RP-F group and assessed pre-operatively and at one year post-operatively. The mean post-operative non-weight-bearing flexion was 107° (95% confidence interval (CI) 104° to 110°)) for the FB-S group and 113° (95% CI 109° to 117°) for the RP-F group, and this difference was statistically significant (p = 0.032). However, weight-bearing range of movement during both level walking and ascending a slope as measured during flexible electrogoniometry was a mean of 4° lower in the RP-F group than in the FB-S group, with 58° (95% CI 56° to 60°) versus 54° (95% CI 51° to 57°) for level walking (p = 0.019) and 56° (95% CI 54° to 58°) versus 52° (95% CI 48° to 56°) for ascending a slope (p = 0.044). Further, the mean post-operative pain score of the Western Ontario and McMaster Universities Osteoarthritis Index was significantly higher in the RP-F group (2.5 (95% CI 1.5 to 3.5) versus 4.2 (95% CI 2.9 to 5.5), p = 0.043). Although the RP-F group achieved higher non-weight-bearing knee flexion, patients in this group did not use this during activities of daily living and reported more pain one year after surgery.

Correlates of knee laxity change in early rehabilitation after anterior cruciate ligament reconstruction.

Factors other than ligament graft length (knee ROM, knee swelling, initial knee laxity) may need to be accounted for in interpreting changes in knee laxity during rehabilitation following anterior cruciate ligament reconstruction (ACLR) surgery. Twenty-three patients recovering from ACLR surgery (16 M, 7 F, age mean = 30) were tested at 2 and 6 weeks after ACLR with knee laxity measured using th Knee Signature System arthrometer, passive ROM with a standard goniometer and swelling by measuring knee circumference at the mid-patella level using a cloth measuring tape. Spearman correlation coefficients (in parentheses) were calculated using rankings of the change in the injured minus uninjured knee laxity as the dependent variable and the following independent variables: pre-test injured minus uninjured knee laxity (ranked; -0.457; statistically significant two-tailed P < 0.05); change in injured knee maximum extension relative to the uninjured side (ranked; 0.127); change in injured knee maximum flexion relative to the uninjured side (unranked; -0.073); and change in the injured minus uninjured knee girth (unranked; -0.159). These results indicate that consideration should be given to the patient's knee laxity at the start of intervention when using changes in laxity to guide rehabilitation after ACLR.

Effects of open versus closed kinetic chain training on knee laxity in the early period after anterior cruciate ligament reconstruction.

Knee extensor resistance training using open kinetic chain (OKC) exercise for patients recovering from anterior cruciate ligament reconstruction (ACLR) surgery has lost favour mainly because of research indicating that OKC exercise causes greater ACL strain than closed kinetic chain (CKC) exercise. In this prospective, randomized clinical trial the effects of these two regimes on knee laxity were compared in the early period after ACLR surgery. Thirty-six patients recovering from ACLR surgery (29 males, 7 females; age mean = 30) were tested at 2 and 6 weeks after ACLR with knee laxity measured using the Knee Signature System arthrometer. Between tests subjects trained using either OKC or CKC resistance of their knee and hip extensors in formal physical therapy sessions three times per week. Following adjustment for site of treatment, pretraining injured knee laxity, and untreated knee laxity at post-training, the use of OKC exercise, when compared to CKC exercise, was found to lead to a 9% increase in looseness with a 95% confidence interval of -8% to +29%. These results indicate that the great concern about the safety of OKC knee extensor training in the early period after ACLR surgery may not be well founded.

Some effects of camera placement on the accuracy of the Kinemetrix three-dimensional motion analysis system.

OBJECTIVE: To assess the accuracy of the Kinemetrix motion analysis system to measure horizontal movement by a single reflective marker away from two cameras with differing camera placements. DESIGN: Trial of the effects of nine different camera arrangements on precision of non-human movement. BACKGROUND: In many cases the ability to arrange cameras to allow a separation of 60 degrees is not possible. Little is known about the precision of motion analysis systems for small camera angle separations. METHODS: The accuracy of the Kinemetrix system was assessed with camera horizontal separations of 15 degrees, 30 degrees and 45 degrees, and vertical separations of 0 degrees, 15 degrees and 30 degrees rendering nine different camera placements. The distance between the cameras and the object was always maintained at 4 m. During each test the marker was moved a known horizontal distance along a line bisecting the horizontal angular separation of the two cameras. The mean absolute errors of the Kinemetrix measurement were calculated. RESULTS: At the smallest camera separation tested (15 degrees horizontal, 0 degrees vertical), the Kinemetrix was unable to calculate the three-dimensional co-ordinate of the marker. For all other camera positions tested, the errors in measurements were small (mean absolute errors < 2 mm). CONCLUSIONS: Maintaining camera horizontal and vertical separations above a sum of 30 degrees is sufficient for clinical testing. RELEVANCE: Motion analysis systems are becoming more common for clinical evaluation where only confined testing areas are available. These confined areas often make positioning of cameras at greater than 60 degrees impossible; therefore, there is a need to explore the errors involved in placing two cameras at less than 60 degrees.