Nociceptive phenotype alterations of dorsal root ganglia neurons innervating the subchondral bone in osteoarthritic rat knee joints.

OBJECTIVE: Subchondral bone plays a role in generating knee joint pain in osteoarthritis (OA). The objective of this study was to clarify nociceptive phenotype alterations of subchondral bone afferents of the distal femur in mono-iodoacetate (MIA)-induced OA rats. METHODS: OA was induced by intra-articular injection of MIA in rats. Two different retrograde tracers were separately injected into the knee joint cavity and the subchondral bone to identify joint and subchondral bone afferents. Immunohistochemistry was used at 2 weeks (early stage) and 6 weeks (advanced stage) after MIA injection to determine the expression of nociceptive markers (calcitonin gene-related peptide (CGRP) and tyrosine receptor kinase A (TrkA)) and the soma size distribution of CGRP-immunoreactive (IR) neurons. Histological subchondral bone and cartilage damage was scored according to the Osteoarthritis Research Society International grading system. Pain-related behavior was evaluated using weight distribution and mechanical sensitivity of the hind paw. RESULTS: OA caused an up-regulation of CGRP, TrkA and enlargement of soma size of CGRP-IR neurons in both joint and subchondral bone afferents. CGRP and TrkA expression in subchondral bone afferents gradually increased over 6 weeks. Furthermore, up-regulation of CGRP and TrkA in subchondral bone afferents displayed a strong correlation with the subchondral bone damage score. CONCLUSION: Up-regulation of nociceptive markers in subchondral bone afferents correlated with subchondral bone damage, suggesting that subchondral bone is a therapeutic target, especially in the case of advanced stage knee OA. In particular, CGRP and TrkA are potentially molecular therapeutic targets to treat joint pain associated with subchondral lesions.

Determining the rotational alignment of the tibial component at total knee replacement: a comparison of two techniques.

We prospectively assessed the benefits of using either a range-of-movement technique or an anatomical landmark method to determine the rotational alignment of the tibial component during total knee replacement. We analysed the cut proximal tibia intraoperatively, determining anteroposterior axes by the range-of-movement technique and comparing them with the anatomical anteroposterior axis. We found that the range-of-movement technique tended to leave the tibial component more internally rotated than when anatomical landmarks were used. In addition, it gave widely variable results (mean 7.5 degrees ; 2 degrees to 17 degrees ), determined to some extent by which posterior reference point was used. Because of the wide variability and the possibilities for error, we consider that it is inappropriate to use the range-of-movement technique as the sole method of determining alignment of the tibial component during total knee replacement.

Total hip arthroplasty with a sliding iliac graft for acetabular dysplasia.

We describe a new technique of reconstruction of the deficient acetabulum in cementless total hip arthroplasty. The outer iliac table just above the deficient acetabulum is osteotomised and slid downwards. We have termed this an iliac sliding graft. Between October 1997 and November 2001, cementless total hip arthroplasty with an iliac sliding graft was performed on 19 patients (19 hips) with acetabular dysplasia. The mean follow-up was 3.4 years (2 to 6). The mean pre-operative Harris hip score was 45.1 which improved significantly to 85.3 at the time of the final follow-up. No patient had post-operative abductor dysfunction. Incorporation of the graft was seen after two to three months in all patients. Resorption of the graft and radiolucencies were infrequent. This technique is a useful alternative to femoral head autografting when the patient's own femoral head cannot be used.