Jan Kuiper

Hip resurfacing for rheumatoid arthritis: independent assessment of 11-year results from an international register

Total hip replacement has shown good outcomes for patients with rheumatoid arthritis. Can hip resurfacing give similar results for patients with rheumatoid arthritis? Using an international hip resurfacing register, 47 patients with rheumatoid arthritis were identified and age and gender matched to a group of 131 randomly selected patients with osteoarthritis of the hip joint. Patients completed a questionnaire to record function and implant revision. Hierarchical regression, Cox regression and Kaplan-Meier method were used for analysis. There was a significant increase in post operative hip score in both groups (p < 0.001) with rheumatoid group scoring higher as compared to the osteoarthritis group (p = 0.23). The post operative score was not significantly influenced by pre-operative score and age (p = 0.15 and 0.84, respectively) but the pre-operative score was a predictor of implant failure (p = 0.02). Patient mobility was affected by age with younger patients scoring high on mobility as compared to older patients (p = 0.01). The Kaplan-Meier analysis showed a survival rate of 96.3% in the rheumatoid group and 97.8% in the osteoarthritis group. This difference was not significant (Log rank test, p = 0.45). Our results from an independent and international register show that hip resurfacing provides good post-operative hip function and excellent implant survival for patients with rheumatoid arthritis of the hip joint. This procedure can be considered as a viable option for management of rheumatoid arthritis of the hip joint.

Mechanical characteristics of three staples commonly used in foot surgery

BackgroundBone staples are an accepted method of fixation in foot surgery. They reduce operating time and trauma in surgical procedures. A variety of memory staples are available but their properties compared to standard staples are not known. We carried out a study comparing two popular types of memory staples and a standard stainless steel staple.MethodsStandardized bone models of metatarsals made from Tufnol tubes were osteotomized and stabilised using one of three types of bone staples, two types of memory staple (Memory staple and heat-activated Memoclip) or a standard stainless steel staple (Richards). Constructs were loaded in bending and torsion on a material testing machine. The moment and torque to achieve 10 degree of bending or torsion and permanent angulation of the osteotomized bones were assessed.ResultsThe Richards staple was found to provide a four times larger resistance to bending and torsion than the two memory staples. However, it was permanently deformed after bending. The Memory and Memoclip staples were equal in their stiffness. In addition, angulation of bones fixed with the Memoclip was elastic, preventing any permanent deformation.ConclusionThe Richards staple was stiffer, although the permanent deformation of this staple is a disadvantage. Memoclip staples exhibit lower but adequate stiffnesss when compared to the standard Richards staple and are not permanently deformed after bending. The Memoclip staples were easier to handle. The results will enable surgeons to determine the optimal staple for foot and ankle procedures.

Predicting In Vivo Clinical Performance of Anterior Cruciate Ligament Fixation Methods From In Vitro Analysis Industrial Tests of Fatigue Life and Tolerance Limits Are More Useful Than Other Cyclic Loading Parameters

Background Anterior cruciate ligament graft fixations experience cyclic loads in vivo. Present cyclic loading studies testing fixation use “incremental cycling,”“residual strength” protocols, or a combination. Industrial standards, however, rely on fatigue life testing and use tolerance limits to determine guaranteed minimum levels of cycles to failure. Hypothesis Industrial standards of fatigue life and lower tolerance limits provide a more conservative assessment of cycles to failure than do currently used cyclic loading models, and they facilitate interpretation of data toward clinical performance. Study Design Descriptive laboratory study. Methods Fatigue life curves and lower tolerance limits were calculated for porcine patellar tendon graft fixations that were tested to failure in single pulls or cycled to failure at 2 different load levels. A log curve was constructed so that the expected values at other load levels could be calculated. Comparison of a metal and a composite resorbable interference screw design was used as an example. Results Cycles to failure of both screw designs varied widely at each load level. The guaranteed minimum number of cycles calculated by tolerance limits was therefore much lower than the mean cycles to failure at any given load level. For example, at a load of 250 N, the predicted mean life for the composite screw and the metal screw was 2513 and 1490 cycles, respectively, whereas the 80/80 tolerance limits (the value that 80% could be expected to achieve with 80% confidence) were only 63 and 68 cycles, respectively. Small reductions in load level gave very large increases in minimally expected life. Conclusions Fatigue testing of anterior cruciate ligament reconstructions better shows the wide variation between specimens and the large effect of load levels on expected life. Wide scatter makes mean levels overoptimistic and difficult to interpret. Tolerance limits give estimates that are more conservative and facilitate data interpretation. Clinical Relevance A method for testing and analyzing fatigue properties was presented, results of which are more readily interpreted to clinical practice.

Biomechanical analysis of tension band wiring (TBW) of transverse fractures of patella

Purpose Tension band wiring is commonly used for fixation of simple transverse fractures. The popular configuration is parallel Kirschner wires (K-wires) and a stainless steel wire loop placed in a vertically oriented figure-of-8. Methods We used a wooden model of a patella with a midway transverse fracture and compared four different types of fixation. The first construct had a vertical figure-of-8 with one twist of wire. The second contained a vertical figure-of-8 with two twists of wire. The third was a vertical figure-of-8 with two twists of wire placed at adjacent corners while the last one had a horizontal figure-of-8 with two twists of wire placed at adjacent corners. Interfragmentary compression at the point of wire breakage was measured for each construct as well as permanent displacement on cyclic loading. Results Placement of the figure-of-eight in a horizontal orientation with two wire twists at the corner improved interfragmentary compression by 63% (p < 0.05, Tukey post hoc test). On cyclic loading, all the constructs with vertical figure-of-eight but none with a horizontal construct failed (p = 0.01; Fishers exact test). Permanent fracture displacement after cyclic loading was 67% lower with horizontal figure-of-eight constructs (p < 0.05; t test). Conclusion Placing wire twists at the corner and a horizontal placement of figure-of-8 improves stability of the construct.

External rotation bracing for first-time anterior dislocation of the shoulder: A discontinued randomised controlled trial comparing external rotation bracing with conventional sling

Introduction Itoi et al. introduced the concept of bracing in abduction and external rotation to treat traumatic anterior shoulder dislocations. However, controversy remains as studies have reported variable results. Our study investigates whether there is a difference in outcomes between treatment with a conventional sling or external rotation brace. Methods A prospective, multi-centre randomised control trial was conducted between 2006 and 2010. The study was discontinued early with 72 (36 cases in each group) first-time anterior shoulder dislocations recruited. Results The re-dislocation rate over 24 months was comparable 30% (95% CI: 17–47) sling vs. 24% (95% CI: 13–41) external rotation bracing. Sixteen percent (95% CI: 7–32) of sling patients and 12% (95% CI: 5–27) of external rotation-bracing patients had shoulder stabilisation surgery within 24 months of the initial dislocation (p > 0.05). There was no difference in OSI scores at 24 months between the two treatment groups and intolerability of the external rotation brace was high. Conclusion Recruitment to this study was difficult, and lost-to-follow-up rates were high leading to early discontinuation of the study. The results suggest that ER bracing is unlikely to provide clinical benefit in traumatic first-time anterior shoulder dislocation.

Low failure rate at short term for 40 mm heads and second generation triple annealed HCLPE liners in hybrid hip replacements

Introduction 40 mm large diameter heads offer the advantages of lesser dislocation rates and better stability while highly cross linked polyethylene have lower wear rates than ultra high molecular weight polyethylene. Studies of the survivorship of 40 mm heads in hybrid hip replacements with Exeter stem and second generation highly cross linked polyethylene are limited. The purpose of the study is to report the short term of survivorship of the large diameter heads (40 mm) with Exeter stem with the secondary aim being the survival analysis of the thinnest second generation highly cross linked polyethylene. Methods Retrospective case series of survivorship of patients with hybrid hip replacements of Exeter stems with 40 mm heads articulating with second generation triple annealed highly cross linked polyethylene liner on a uncemented acetabular shell was performed. As a subset, survival of thinnest second generation highly cross linked polyethylene survival (3.8 mm) at short term was assessed. Survival of the implants was confirmed from the hospital records and National joint registry as of 2015. Revision for any cause was taken as end point. Results 324 hybrid hip replacements with 40 mm heads had been performed for primary hip osteoarthritis. Of the 324 hip replacements, 154 hip replacements had thinnest second generation highly cross linked polyethylene (3.8 mm). Two patients had revision of components, one for periprosthetic fracture and one for deep infection. Mean age of the patients was 70.5 years (range 42-88 years, median 71, SD 8.3 years). None of the patients had revision due to trunion wear or loosening of components. The overall 5-year implant survival probability of hips with 40 mm heads was 99.4% (95% CI 98 to 100%) while the subset group of hip replacements with thinnest second generation highly cross linked polyethylene (3.8 mm) had 5-year implant survival probability of 99.3% (95% CI 97.1 to 100%). Conclusion Short term survivorship does not show significant evidence of early failure or higher rate of revision in our series of hybrid hip replacements with large diameter heads and second generation triple annealed highly cross linked polyethylene. Dislocation rate at the short term is none. Results from this series have to be carefully interpreted due to the relatively short follow up but so far results are encouraging. Long term follow up is required to conclude whether there is early or higher rate of failure. It is our intention to follow up this cohort and further publish our results at longer term.