The modified technique for paraspinous muscle flap surgery is based on several basic principles of wound healing: the establishment of an adequate blood supply to the wound, aggressive and effective debridement, and wide suction drainage. The cornerstone of the modified technique is the Lembert suture variation. This method of suturing was first introduced by Antoine Lembert, a French, 19th century surgeon, in 1826. The technique was developed as a means to carefully approximate the serosal surfaces of small bowel in hand-sewn anastomoses.10
This method of suturing is widely used, to this day, in bowel anatomoses as well as in various gynecologic surgeries. We have adopted this technique for this particular procedure because the geometry of the suture imbricates the paraspinous muscle into the wound defect, effectively obliterating the dead space around the spinal hardware.
We first begin by aggressively debriding all skin, subcutaneous tissue, muscle, and bone in the wound bed (Fig a). All soft tissue is debrided using the Versajet Hydrosurgery System (Smith and Nephew, London, UK). Soft tissue is debrided until it appears healthy and well perfused. Special attention is paid to the medial edge of the paraspinous muscles. This tissue is frequently macerated and necrotic as a result of the initial instrumentation and subsequent infection. Each spinous process in the wound bed is debrided using a rongeur. Next, the wound is pulse lavaged with several liters of bacitracin-impregnated isotonic sodium chloride solution. After adequate irrigation, the subcutaneous tissue is elevated 5 to 7 cm over the paraspinous muscles, keeping the fascia intact. The fascia is then released lateral to each of the paraspinous muscles, allowing the bellies to advance medially. Two Blake drains are placed along the length of the wound in the submuscular space (Fig b). The paraspinous muscles are then imbricated over the drains using the interrupted Lembert suture technique with buried, no. 1 PDS sutures (Ethicon, Somerville, NJ, US). The suture enters the medial aspect of the longissimus muscle, travels laterally within the muscle, and exits at the lateral aspect of the longissimus; the suture then reenters the musculature at the lateral edge of the longissimus muscle on the contralateral side, travels medially within the muscle, and exits at the medial aspect of the longissimus muscle (Fig a). Special attention must be paid so that the suture is not allowed to exit the medial edge of the spinalis muscle, as would happen in the classic approach. When the suture is tied, the medial portion of the paraspinous muscle group (the spinalis muscle) is forced into the wound defect, obliterating the dead space around the hardware and creating a well-vascularized wound bed (Fig b). In the classic approach, the paraspinous muscles are simply approximated at the midline, tenting the musculature and leaving a large dead space between the muscle, vertebral body, and hardware. Finally, 2 more Blake drains are placed in the subcutaneous space. Scarpas fascia is closed with interrupted, buried, no. 1 PDS suture followed by 3.0 Monocryl (Ethicon, Somerville, NJ, US) in the deep dermis and finally staples on the skin (Fig d).
Figure 1 Step-wise progression of the modified paraspinous muscle flap technique. (a) The wound is aggressively debrided and irrigated. (b) The paraspinous muscles are elevated and 2 drains are placed in the submuscular space. (c) The paraspinous muscles are advanced (more ...)
Figure 2 Sketches of the Lembert suturing technique used in the modified paraspinous muscle flap and the effect it has on the paraspinous musculature. (a) The suture enters the medial longissimus muscle, exits at the lateral aspect of the longissimus and then (more ...)
In comparing the modified technique group with the classic group, both patient groups demonstrated similar demographics and medical histories, therefore, it is unlikely that either group was predisposed to a higher rate of complications or hardware failure. The modified technique group had fewer postreconstruction wound healing complications requiring hospital readmission and a significantly higher hardware salvage rate (Table ). Postreconstruction wound healing complications that did not require hospitalization included smaller seromas that could be safely drained in the office and minor infections. Hardware was removed after wound reconstruction only if the instrumentation loosened or if it did not become properly incorporated into the bone. These hardware complications are not necessarily mechanical in nature, but, rather, the wound bed must be well vascularized and devoid of inflammatory milieu for spinal instrumentation to become successfully incorporated into the vertebral bodies.11
Therefore, the higher hardware salvage rate associated with the modified technique, combined with the fewer number of reinfections, suggests that this new technique provides a superior wound reconstruction than the classic technique.
Compared with previously published studies on paraspinous muscle flap variations, the modified technique yields excellent results. Our data reveal a high hardware salvage rate (95.4%) and a low rate of wound healing complications requiring hospital readmission (13.6%; Table ). The hardware salvage rate associated with the classic technique is 37.5% and wound healing complication rates range from 25% to 43%.9,12
The second reported variation, the vest-over-pants technique, was devised as a method to prevent cerebrospinal fistula formation. This study involved 9 patients and reported a wound healing complication rate of 22% and 1/1 hardware salvage rate.6
The Hultman technique is most similar to the modified technique in that both methods result in lateral approximation of the paraspinous muscles. Unlike the Hultman method, the modified technique features aggressive debridement via hydrodissection using the Versajet (Smith and Nephew, London, UK). Hultman et al1
details the outcomes of 25 patients, reporting a wound healing complication rate of 12% and a hardware salvage rate of 64%.1
Given the results from previously published studies, the modified technique appears to have a superior hardware salvage rate and a low rate of postreconstruction wound complications.
This study was inherently limited due to its retrospective design. Inevitably, there was recall bias on behalf of the researcher in collecting the data and on behalf of the surgeon, who was consulted when case clarification was necessary. To eliminate recall bias in the future, we plan to design a prospective study. In this study, patients that possess risk factors known to be associated with a significantly increased wound healing complication rate will be divided into 2 groups. One group will receive prophylactic paraspinous muscle flaps using the modified technique at the time of initial spine surgery and the other group will receive wound reconstruction on an as-needed basis. Later, we will compare the incidence of postreconstruction wound healing complications between the 2 groups. Providing prophylactic flap coverage in at-risk patients could potentially eliminate 2 surgeries: (1) paraspinous flap reconstruction after the development of a nonhealing wound and (2) operative debridement for postreconstruction wound healing complications. This may be an efficacious approach to spinal wound reconstruction in certain patient populations.
When compared with the classic group in this study and other published series of the paraspinous muscle flap procedure, the modified technique appears to improve the hardware salvage rate and decrease the number of wound complications. Furthermore, the modified technique is associated with a shorter mean length of stay than the classic technique. The paraspinous muscle flap remains an important tool in the reconstructive surgeon's armamentarium and this technical variation further improves on the flap's design, resulting in an improved wound healing ability.