An Ultra-Short Femoral Neck-Preserving Hip Prosthesis: A 2-Year Follow-up Study with Radiostereometric Analysis and Dual X-Ray Absorptiometry in a Stepwise Introduction.

BACKGROUND: Total hip arthroplasty (THA) with a diaphyseal stem may risk bone loss. In order to save proximal bone stock in young patients with a high activity level and a long life expectancy, the interest in short stems has evolved. The purpose of this prospective observational cohort study was to evaluate the fixation of, and bone remodeling around, the Primoris femoral neck-preserving hip implant. METHODS: Fifty younger patients with end-stage osteoarthritis were managed with the Primoris hip implant. We evaluated bone mineral density (BMD) using dual x-ray absorptiometry (DXA) and implant migration using radiostereometric analysis (RSA). A region-of-interest (ROI) protocol for 4 ROIs was applied to assess BMD. The association between BMD and migration was evaluated to determine the fixation of the Primoris implant and bone remodeling in the proximal part of the femur. Follow-up evaluation was performed at regular intervals from day 1 (baseline) until 24 months after surgery. RESULTS: The major stem migrations were subsidence (Y axis; mean, 0.38 mm) at 6 weeks and varus tilt (rotation) (Z axis; mean, 0.93°) at 6 to 12 months. In ROI4 (the calcar area), a significant gain in bone was found with a mean difference of 4.1% (95% confidence interval [CI], 0.8% to 7.4%; p < 0.02) at 24 months postoperatively. Significant bone loss was found in ROI1 and ROI2, with a mean difference of -4.9% (95% CI, -7.4% to -2.4%; p = 0.0003) and -8.9% (95% CI, -11.5% to -6.2%; p = 0.0001), respectively. Linear regression and multivariate regression analysis showed a significant negative association between maximal total point motion and BMD (p = 0.02, R = 15%; and p < 0.05, R = 26%, respectively). CONCLUSIONS: The Primoris component showed satisfactory primary stability with promising results at the 24-month follow-up. DXA scans showed limited stress-shielding with the proximal loading pattern of the Primoris. Better bone quality was associated with less implant migration. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Bone remodelling of the proximal femur after total hip arthroplasty with 2 different hip implant designs: 15 years follow-up of the thrust plate prosthesis and the Bi-Metric stem.

INTRODUCTION: The thrust plate prosthesis (TPP) was introduced to preserve bone in patients undergoing total hip arthroplasty. We assessed the long-term results of hip arthroplasty in patients who received the TPP compared to a traditional intramedullary stem (Bi-Metric). METHODS: In this prospective observational cohort study, we evaluated bone mineral density (BMD) using dual-energy X-ray absorptiometry (DXA), radiological imaging and clinical outcome using Harris Hip Score (HHS). Twenty patients received the TPP (group A) and 18 patients received the Bi-Metric stem (group B). Baseline was the 1st postoperative day, and subsequent follow-up was performed at 6 months, 1, 2, 8, 12 and 15 years after surgery. A four regions of interest (ROI) protocol was developed to assess BMD. RESULTS: In ROI1, bone resorption was significantly higher for group A at 6 months with a mean difference of 10% (95% confidence interval [CI], 4-16; p = 0.003) and 8% (95% CI, 1-15; p = 0.03) at 8 years. Regarding ROI4, group A had a lesser decrease in general compared to group B. The radiological findings did not reveal any subsidence or detectable implant migration. HHS improved from 53 (23-69) to 93 (55-100) in group A and from 51 (24-72) to 94 (78-100) in group B. CONCLUSION: The TPP was not found to be inferior to the Bi-Metric stem regarding bone preservation. The decrease in BMD in ROI4 was greater in group B. Clinical and radiological results also revealed that the TPP was not inferior to the Bi-Metric stem.

Tourniquet induced ischemia and changes in metabolism during TKA: a randomized study using microdialysis.

BACKGROUND: Tourniquet use in total knee arthroplasty (TKA) surgery is applied to minimize blood loss thereby creating better overview of the surgical field. This induces ischemia in the skeletal muscle resulting in reperfusion injury. Our aim was to investigate the in vivo metabolic changes in the skeletal muscle during TKA surgery using microdialysis (MD). METHODS: Seventy patients were randomly allocated to tourniquet group (n = 35) or non-tourniquet group (n = 35). Prior to surgery, catheters were inserted in the operated leg and non-operated leg. Interstitial dialysate was collected before and after surgery and at 20 min intervals during a 5 h reperfusion period. Main variables were ischemic metabolites: glucose, pyruvate, lactate and glycerol and L/P ratio. RESULTS: Significant difference in all metabolites was detected between the two groups, caused by tourniquet application. Tourniquet induced ischemia resulted in decreased levels of glucose and pyruvate to 54 and 60 % respectively, compared to baseline. Simultaneously, accumulation of lactate to 116 % and glycerol to 190 % was observed. L/P ratio was elevated indicating ischemia. In the non-tourniquet group the metabolite changes were less profound and normalized within 60 min. CONCLUSIONS: Microdialysis revealed that performing TKA with tourniquet is associated with increased ischemia. This affects all metabolites but the changes are normalized after 5 h.

Absence of a Tourniquet Does Not Affect Fixation of Cemented TKA: A Randomized RSA Study of 70 Patients.

We aimed to determine whether not using a tourniquet in cemented TKA would affect migration of the tibial component measured by radiosterometric analysis (RSA). Seventy patients were randomized into a tourniquet group and a non-tourniquet group and using model-based RSA, the migration of the tibial component was analyzed. Primary and secondary outcome measures were maximum total point motion (MTPM) and translations and rotations. Follow-up period was 2 years. The tibial component was well fixated in both groups and no significant difference in migration between the two groups was detected (P=0.632). Mean MTPM (SD) was 0.47 mm (0.16) in the tourniquet group and 0.45 mm (0.21) in the non-tourniquet group. Absence of tourniquet indicates that stable fixation of the tibial component can be achieved in cemented TKA.

Faster recovery without the use of a tourniquet in total knee arthroplasty.

BACKGROUND AND PURPOSE: Tourniquet application is still a common practice in total knee arthroplasty (TKA) surgery despite being associated with several adverse effects. We evaluated the effects of tourniquet use on functional and clinical outcome and on knee range of motion (ROM). PATIENTS AND METHODS: 70 patients who underwent TKA were randomized into a tourniquet group (n = 35) and a non-tourniquet group (n = 35). All operations were performed by the same surgeon and follow-up was for 1 year. Primary outcomes were functional and clinical outcomes, as evaluated by KOOS and knee ROM. Secondary outcomes were intraoperative blood loss, surgical time and visibility, postoperative pain, analgesic consumption, and transfusion requirements. RESULTS: Patients in the non-tourniquet group showed a better outcome in all KOOS subscores and better early knee ROM from surgery to week 8. No difference was detected at the 6- and 12-month follow-ups. Postoperative pain and analgesic consumption were less when a tourniquet was not used. Surgical time and visibility were similar between groups. Intraoperative blood loss was greater when not using a tourniquet, but no postoperative transfusions were required. INTERPRETATION: This study shows that TKA without the use of a tourniquet results in faster recovery in terms of better functional outcome and improved knee ROM. Furthermore, reduced pain and analgesic use were registered and no intraoperative difficulties were encountered.

Variability of three-dimensional forces increase during experimental knee pain.

Knee pain is a common symptom of different knee pathologies, affecting muscle strength and force generation. Although the control of precise three-dimensional forces is essential for the performance of functional tasks, current evidence of pain effects in force variability is limited to single-directional assessments of contractions at moderate force levels. This study assessed the effects of experimental knee joint pain in the three-dimensional force variability during isometric knee extensions at a wide range of target forces (2.5-80 % of maximal voluntary contraction, MVC). Fifteen healthy subjects performed contractions before, immediately following, and after injections of hypertonic (painful) or isotonic (control) saline into the infrapatellar fat pad. Pain intensity was measured on a 10-cm visual analogue scale. Force magnitude, direction, and variability were assessed using a six-axis force sensor while activity of quadriceps and hamstring muscles was recorded by surface electromyography. Significant correlation was found between tangential force displacements and variability of quadriceps muscle activity. Experimental knee pain increased the variability of the task-related force component at all force levels, while variability of tangential force components increased at low forces (≤5 % of MVC). The mean quadriceps activity decreased during painful contractions only at 80 % of MVC. Pain adaptations underlying increased force variability at low contraction levels probably involve heterogeneous reorganization of muscle activity, which could not be detected by surface electrodes. These findings indicate a less efficient motor strategy during knee joint pain, suggesting that pain relief may enhance training for the control of smooth forces by knee pain patients.