Impact of keel saw blade design and thickness on the incidence of tibial plateau fracture and tibial implant-loosening in cementless medial UKR.

BACKGROUND: Tibial plateau fractures and tibial implant- loosening are severe complications in cementless unicompartmental knee replacement (UKR). The tibial keel preparation is particularly demanding and different saw blades can be used. It was hypothesized that different blade designs and thickness have an influence on the frequency of tibial plateau fractures and implant-loosening in cementless medial UKR. METHODS: 1258 patients with cementless medial UKR were included in this retrospective study between 2013 and 2020. The tibial keel cut was performed either with a double keel saw blade (DKS; 2.8 mm) and added hand guided pick or a mono reciprocating saw blade (RKB) of different thickness (2.5 mm; 2.65 mm; 2.75 mm). Tibial plateau fracture and loosening were demonstrated by standard two-plane radiographs. Tibial implant-loosening was defined as complete radiolucency and implant migration. Fracture and loosening were combined with pain and loss of function. RESULTS: In 126 patients (10%) the tibial keel was prepared with DKS, in 407 patients (32.4%) with RKB 2.5 mm, in 330 patients (26.2%) with RKB 2.65 mm and in 395 patients (31.4%) with 2.75 mm. In 4 patients (3.17%) with DKS tibial plateau fracture occurred, in 4 patients (0.99%) with 2.5 mm RKB, in 3 patients (0.92%) with 2.65 mm RKB and in 1 patient (0.25%) with 2.75 mm RKB. Significantly fewer fractures occurred with a RKB design (p = 0.007). A negative correlation between fracture incidence and RKB saw blade thickness was found (Spearman-r = - 0.93). No difference for tibial implant-loosening was shown (p = 0.51). CONCLUSION: Different blade designs and thickness have a significant influence on the incidence of tibial plateau fractures and aseptic tibial implant-loosening. The incidence of tibial plateau fractures in cementless medial UKR can be reduced by changing the design and thickness of the tibial keel saw blade. Greater thickness of RKB leads to significantly fewer tibial plateau fractures while the incidence of implant-loosening is not increasing. TRIAL REGISTRATION: This study was retrospectively registered and ethical approval was waived by the local ethical committee (No. 2020-1174).

Implantation Accuracy of a Lateral Unicompartmental Knee Arthroplasty: A Hoffa´s Fat Pad-Preserving Medial Approach Versus the Transpatellar Lateral Approach.

BACKGROUND: A small proportion of patients suffer from isolated lateral osteoarthritis where the sole lateral unicompartmental knee arthroplasty (UKA) is a possible treatment option. There, both a medial and a lateral surgical approach can be considered. This study should answer the question whether the lateral approach is superior to a modified medial approach in terms of implantation accuracy and subjective outcome. METHODS: In this retrospective study, 175 patients with lateral UKA were included between 2015 and 2020. In 82 patients, the lateral approach was used, and in 93 patients, the medial approach was used. To assess implantation accuracy, different imaging criteria on postoperative radiographs were analyzed. Postoperative patient-related outcome measurements (PROMs) (OKS, LEFS, and EQ5D) were evaluated. Statistical significance was assumed for P < .05. RESULTS: The tibial implant relation to the tibial plateau diameter in the lateral approach was significantly larger than in the medial approach (23.6% vs 22.2%; P < .001). Significantly more deviations >15° regarding flexion position of the femoral implant (P = .002) and a higher number of deviations of the slope was found (P = .06) in the lateral approach. The lateral approach showed a significantly higher rate of lateral positioning of the femoral component (P = .007). Post-PROMs showed significant improvement in both approaches. CONCLUSION: The lateral approach is not superior regarding different radiological accuracy criteria. The Hoffa´s fat pad-preserving medial approach showed good results in implantation accuracy and therefore is a good alternative to implant lateral UKA. In addition, significant improvement in PROMs could be demonstrated.

Primary Total Hip Arthroplasty in Severe Dysplastic Hip Osteoarthritis With a Far Proximal Cup Position.

BACKGROUND: Developmental hip dysplasia is the most common cause of secondary hip osteoarthritis. Due to severe acetabular bone deficiency, cup positioning in total hip arthroplasty (THA) of dysplastic hips remains a surgical challenge. The aim was to analyze the functional outcome of far proximal cup positions in primary THA. METHODS: Fifty patients (61 hips) with THA for severe dysplastic osteoarthritis and a far proximal cup position were included. Patients were divided according to the heights of the implanted cups with increasing vertical distance from the interteardrop line (group A: 55-65 mm, group B: 65-75 mm, group C: >75 mm). Functional outcome was assessed at latest follow-up (38 ± 16 months) by Lower Extremity Functional Score, Tegner Activity Score, and Harris Hip Score (HHS). Patients answered a Patient Satisfaction Questionnaire. Leg length discrepancy was estimated radiographically. RESULTS: The Lower Extremity Functional Score significantly decreased in C (45.3 ± 25) compared to A (66.7 ± 15.3) and B (67.9 ± 9.9). The Tegner Activity Score significantly increased in all subgroups from preoperative to postoperative (2.2 ± 1.3 to 4.1 ± 1.4; P < .05). The mean overall HHS was 89.3 ± 14.7 (A: 89.5 ± 14.3, B: 94.3 ± 6.5, C: 78.3 ± 22.1). The HHS domains of activity of daily life and gait were significantly reduced in C (P < .05). Patients described a high satisfaction level with the surgery. No significant differences were found with regard to preoperative and postoperative leg lengthening (P = .881). Neither dislocations, impingement problems nor neurologic complications were observed. CONCLUSION: Primary THA without any concomitant surgical interventions with a far proximal cup position offers a safe and effective treatment option in severe dysplastic hip osteoarthritis.

Radiosynoviorthesis for treating recurrent joint effusions after endoprosthetic knee replacement.

PURPOSE: Radiosynoviorthesis (RSO) has been established as a treatment modality for rheumatoid arthritis. Other forms of joint diseases like recurrent joint effusions after knee arthroplasties are under investigation. The aim of this study was to examine whether RSO therapy is effective in the application of an endoprosthesis and whether there are common causes of failure. MATERIALS AND METHODS: Between 1998 and 2005, 55 patients received RSO treatment (90Y colloid) for recurrent joint effusions after endoprosthetic knee replacement. A total of 46 patients were followed up and questioned anonymously according to a modified Knee Society Knee Scoring System (KSS) and Hospital for Special Surgery score. On the basis of patient records, a subgroup analysis of patients with revision surgery after RSO (subgroup A) and without further operative interventions (subgroup B) was performed. RESULTS: Subgroup A comprised 46% (21/46) and subgroup B comprised 54% (25/46) of all patients. Most patients from subgroup A did not benefit from RSO. Of these 21 patients, 7 presented with low-grade infection, 7 presented with signs of endoprosthetic loosening, 2 presented with metal allergy, and 2 had undergone revision because of trauma.Patients in subgroup B experienced a significant improvement in pain (KSS score, from 22.5 to 34 points) and function (KSS score, from 62.9 to 77.3 points; Hospital for Special Surgery score, from 30.2 to 38.7) after RSO. CONCLUSIONS: Radiosynoviorthesis resulted in an improvement in pain and function in ∼50% of patients with knee endoprostheses. In 85% of all patients, in whom RSO treatment failed, endoprosthetic complications like infection, loosening, allergy, and trauma were detected. In conclusion, RSO is a valid therapeutic option for joint effusions after knee arthroplasties. However, if RSO fails, a thorough exclusion of endoprosthetic complications should be performed.