Masaru Nakamura

Retrospective study of deep surgical site infections following spinal surgery and the effectiveness of continuous irrigation

Surgical site infection (SSI) is an unfortunate and unpreventable complication of any surgical intervention including spinal surgery. Early deep SSI (EDSSI) after instrumented spinal fusion are particularly difficult to manage due to the implanted, and possibly infected, instrumentation. The purpose of this study is to retrospectively review patients who underwent spinal surgery, investigate the rate of EDSSI, identify patient-related and surgery-related risk factors and to assess the effectiveness of continuous indwelling irrigation on the eradication of these infections. A total of 814 patients (319 women and 495 men) who underwent spinal surgery were enrolled. Mean age at the initial surgery was 57.4 years old. Infections that penetrated the deep fascia within 1 month after the initial operation were considered as EDSSI. The rate of EDSSI, causal organisms, infection management and resolution were studied. Furthermore, we examined the patient-related and the operation-related risk factors. An overall incidence of EDSSI of 1.1% was found. In 177 patients with diabetes mellitus (DM), two patients (1.1%) developed EDSSI. In 28 patients receiving chronic haemodialysis (HD), two patients with infections (7.1%) were identified, which was statistically significantly greater than the other patient populations. Both operative time and intraoperative blood loss were significantly greater in patients with EDSSI than in non-infected patients. Furthermore, the rate of EDSSI in patients undergoing instrumented spinal fusion (3.8%) was significantly higher than that in the other patients. In the nine patients who developed EDSSI, the causal organisms were identified and treated by surgical debridement, antibiotic therapy and continuous indwelling surgical site irrigation. All infections resolved, and no recurrence has been observed at final follow-up. Removal of the instrumentation was required in only one patient. Based on our results, we believe that continuous surgical site irrigation is an effective adjunct in the surgical treatment for early SSI following spinal surgery.

Clinical outcomes of spinal surgery in patients treated with hemodialysis.

Study Design: Retrospective study. Objective: The purpose of this study is to review clinical outcomes, including survival rate, and to discuss the potential benefit of surgical treatments for spinal disorders in patients treated with long-term hemodialysis (HD). Summary of Background Data: Long-term HD is known to possibly cause destructive spondyloarthropathy (DSA) with spinal canal stenosis. There have been few reports, however, regarding clinical outcomes and patient survival rates after spinal surgeries in this population. Methods: We retrospectively reviewed 33 chronic HD patients who underwent 21 cervical and 13 lumbar spinal surgeries. According to the radiologic findings, we divided them into the non-DSA and the DSA groups. In general, only decompression was performed for the non-DSA patients, whereas spinal fusion was added for the DSA patients. We analyzed the following data, respectively: male-female ratio, age, operative time, estimated blood loss, duration of HD, follow-up duration, preoperative and postoperative Japanese Orthopaedic Association score, improvement ratio of the Japanese Orthopaedic Association score, amyloid deposition characteristics, and survival rate. Results: All patients improved neurologically and functionally after surgery. There were significant differences in the operative time between the DSA and the non-DSA groups in patients with cervical spinal lesions, whereas in patients with lumbar spinal lesions, there were significant differences in sex, operative time, and estimated blood loss. Amyloid deposition was found signficantly more commonly in DSA than in non-DSA patients and was associated with a longer duration of HD. Nine patients died within 49 months of the surgery because of HD-related complications, but there was no surgery-related morbidity. Kaplan-Meier analysis showed a trend toward decreased survival rate in non-DSA patients more than 40 months after the index surgery. Conclusions: Even in patients treated with long-term HD, spinal surgeries reliably obtain neurological and functional improvement if surgeons judge the preoperative inclusion criteria correctly. However, if surgeries are necessary for these patients, surgeons should consider the patients’ comorbidity-related survival rate after the spinal surgeries.

Failure rates of Asian-type anatomic medullary locking stemmed metal-on-metal total hip replacement: A cause for adverse tissue reactions to metal debris (ARMD)

BACKGROUND Adverse tissue reaction to metal debris (ARMD) as a secondary complication of Metal-on-metal total hip replacement (MoM THR) has been of concern. We have been performing cementless MoM THR using an Asian-type anatomic medullary locking (AML) stem. The purpose of this study is to examine the incident rate of ARMD, and the implant survival rate. METHODS The study included 187 patients (211 hip joints) who underwent MoM THR between February 2007 and November 2009 at our hospital and who were followed up for a minimum of 6 years. The cases included 174 female joints and 37 male joints. The average age at the time of surgery was 68.4 years. The average postoperative follow-up period was 87.5 months. RESULTS ARMD was observed in 23 joints postoperatively, and the incidence rate was 10.9%. Most of the instances occurred within the first 30 months postoperatively. Revision surgery was performed for 14 joints after conservative treatment failed, and we changed the bearing surface. During the intraoperative observation, black-colored deposition of metal debris on the head-neck junction was observed in 13 cases. Kaplan-Meier analysis using the replacement surgery as the end point showed that this implant has a survival rate of 93.8% 7 years after the primary surgery. CONCLUSIONS We conclude that the major cause of failure of Asian-type AML stemmed MoM THR is likely the breakage of the fixation between the taper neck and metal head at the head-neck junction.

Chondrogenesis in the synovial tissue is associated with the onset of pseudogout after total knee arthroplasty

Postoperative pseudogout after total knee arthroplasty (TKA) is very rare, and its physical findings are very similar to infectious symptoms. In pseudogout, the mechanism underlying the deposition of calcium pyrophosphate dehydrate crystals remains unclear. Here, we report the histologic findings in a pseudogout attack in the late postoperative period after TKA. She had acute onset of arthritis of the knee 2 years after TKA. Histologic examination showed significant neutrophil infiltration. Interestingly, chondrogenesis was noted in the synovial tissue, and calcium pyrophosphate dehydrate crystals were synthesized mainly at the site of chondrogenesis, suggesting a potential mechanism underlying the occurrence of pseudogout after TKA.