Failures in cranioplasty – A clinical audit & review

Abstract

Introduction

Cranioplasty, like any other surgical procedure also comes with risk of complications and failure. Failure of cranioplasty may be early or delayed and further can be attributed to the surgical procedure itself or to the reconstruction material used for the procedure. The aim of this clinical audit is to analyze the causes of failure of 14 cases of cranioplasty procedure.

Materials and methods

This retrospective study analyses the causes of failure of 14 cases of cranioplasty over 8 ​years ​at a tertiary care centre and identifies major etiological factors for failure including local and systemic. Further, a correlation between the reconstruction material used for cranioplasty and failure was studied along with other attributable factors such as systemic status of the patient and other local factors.

Results

The study established that there exists a correlation between failure and the biomaterial used for reconstruction. Various etiological factors like infection, flap break down, fixation protocol and foreign body were identified along with time frame of failure. After failure of cranioplasty, feasibility of a secondary cranioplasty has also been factored into this study, with 8 out of the 14 cases being successfully re-operated.

Conclusion

Cranioplasty is a technically demanding and demands certain levels of operator skill levels. While formulating a treatment plan for reconstruction of cranial defects, one has to tailor make a strategy considering several factors such as systemic condition of the patient, status of the cranial surgical site, etiology behind craniectomy, choice of reconstruction material, duration from craniectomy and age of the patient. Inspite of best efforts and ideal reconstruction attempts, failures remain a nagging reality.

1. Introduction

Cranioplasty or reconstruction of an existing cranial defect is an established and routinely carried out surgical procedure. Failure of cranioplasty where the reconstruction material has to be removed is the worst type of post operative complication in cranial reconstruction. It may be early postoperative failure (within 5–7 days) or delayed/late (2–3 years). Literature has reported statistics of failures,^{1, 2, 3, 4, 5} but evidence around reasons of failure has not been extensively documented. The authors have attempted to address this lacuna by elaborating on specific causes of failure of cranioplasty in their cases. Early failure is primarily due to infection. Various etiological factors for delayed or late failure are dehiscence, flap breakdown, implant reaction, migration, extrusion, and presence of foreign body like suture material or cottonoid. Re-use of the same biomaterial is not possible after failure. After discarding the preserved bone flap or autogenous bone graft used in the cranioplasty procedure, there may not be sufficient graft material for future reconstruction. Failure has serious repercussions both on the patient as well as the reputation of the operating surgeon while increasing the financial burden. Redoing of cranioplasty is difficult and technically challenging.

2. Aim & objectives

The aim of this clinical audit is to analyze the causes of failure of 14 cases of cranioplasty procedure. The objectives are to establish any correlation between failure and the types of reconstruction material used as well as to ascertain the feasibility of secondary reconstruction.

3. Material and methods

This retrospective study was conducted at a tertiary care referral hospital from Jan 2009 to Dec 2017. The study included failed cases of cranioplasty operated at our center and referred from other centers. Inclusion criteria were cases undergone cranioplasty after decompressive craniectomy for management of intra cranial bleeds/sub dural hemorrhage/stroke and cases undergone craniectomy for management of intra cranial tumors. Exclusion criteria were cases of craniofacial trauma with comminuted fractures of the calvarium. The cases were jointly evaluated with the neurosurgeon. A total of 156 cases had undergone cranioplasty over the 8 year period with the above inclusion & exclusion criteria. Of these, 14 cases of cranioplasty reporting with failure were included in the study, 10 males and 4 females. The failure patients were in the age group of 18–65 years with an average age of 36.14 years. Calvarial defects were fronto-tempero-parietal (FTP) of similar dimensions with a mean average size of the defect being 15 ​cm ​× ​12 ​cm.

Common presenting sign of failure was infection in the form of pus, either from a draining sinus/multiple draining sinuses or gaping/exposure of the surgical wound (surgical wound breakdown). Culture swab was obtained from the draining sinus or exposed surgical wound. All the required investigations including computed tomography (CT) and pre-anesthetic assessment were carried out. The cases were operated under general anaesthesia for exploration and removal of the reconstruction materials. Wound debridement was carried out. Draining sinus and soft tissue defects were addressed by debridement and advancement of the flap. Vacuum drain was activated, wound sutured and pressure dressing applied. Post operative care was given as per the institutional protocol.

On completion of post operative follow up of 06 months all cases were evaluated for secondary reconstruction. In feasible cases, a re-do/secondary cranioplasty was carried out. After re-do cranioplasty, the cases were then followed up for a minimum period of one year.

Pre operative variable of time of reporting with failure was data of consideration. 1 case presented after 7 days (early failure), whereas 13 cases (including the second time failure case) reported after a duration ranging from 3 months to 2 years 10 months (Mean – 1.6 years). Post op and follow up assessment included clinical assessment for syndrome of the trephined/sunken flap syndrome after removal of the failed cranioplasty reconstruction material, as well as CT after re-do/secondary cranioplasty.

4. Results

Out of a total of 156 cases undergone cranioplasty [Preserved bone flap – 74, polymethyl metha-acrylate (PMMA) - 29, Titanium mesh – 53], 14 patients reported with failure, 10 males and 4 females. The failure patients were in the age group of 18–65 years with an average age of 36.14 years (Table 1). First time failure of reconstruction was seen in 13 cases and only 01 patient had second time failure. Bone flap was used in 06 cases, polymethyl metha-acrylate (PMMA) 05, titanium mesh 01 and combination of bone cement and titanium mesh in 01 case (Table 1). In one case first time failure was following use of bone flap and second time with PMMA implant.

Table 1.

Profile of cranioplasty failure patients.

S No	Age	Sex	Primary Cranioplasty Reconstruction Material	Cause Of Failure	Secondary Cranioplasty	Secondary Cranioplasty Reconstruction Material	Follow Up Duration
1	25	M	PMMA	Infection	Done	Bone Graft (Split Calvarial)	2 years 3 months
2	39	M	PMMA	Flap breakdown	Not done	Nil	2 years 10 months
3	48	M	Preserved bone flap	Bone flap not fixed resulting in extrusion	Done	Titanium Mesh	1 year 8 months
4	35	M	Preserved bone flap	Bone flap not fixed resulting in extrusion	Done	Titanium Mesh	1 year 9 months
5	40	F	Preserved bone flap	Flap breakdown	Not Done	Nil	2 years 3 months
6	24	F	Preserved bone flap	Infected cottonoid	Done	Custom made Titanium implant	1 ​Year 10 months
7	47	M	First time - preserved bone flap Second time – PMMA	Infection	Not Done	Nil	2 years
8	31	M	Titanium mesh with bone cement	Extrusion of bone cement	Done	Titanium Mesh	2 years 3 months
9	65	F	PMMA	Frontal sinus infection	Not Done	Nil	1 year 8 months
10	18	M	PMMA	Poor fitting of PMMA	Done	Custom made Titanium Implant	1 year
11	31	M	PMMA	Infection with draining sinus	Done	Titanium Mesh	2 years
12	65	F	Preserved bone flap	Infection	Not Done	Nil	1 year 9 months
13	34	M	Preserved bone flap	Infection	Done	Bone Graft (Split Calvarial) with Titanium Mesh	2 years 9 months
14	38	M	Titanium mesh	Flap perforation	Not Done	Nil	2 years 2 months

The 13 cases of first time reconstruction failures had early failure (7 ​Days) in one case and delayed failure in 12 cases with time of presenting with failure ranging from 3 months to 2 years 10 months (Mean duration – 1.6 years).

In the second time reconstruction failure case, first cranioplasty had been carried out using preserved craniectomy bone flap, which had failed after 5 months. The second cranioplasty had been carried out using a PMMA acrylic cranial plate which had failed after 3 months of the redo cranioplasty procedure.

For statistical break-up, out of 14 failure cases, 6 cases were of autogenous bone (preserved bone flap) and 8 cases had undergone cranioplasty using alloplast material. Alloplast cranioplasty failure cases can be further split into 2 groups – Group A (failure with PMMA cranioplasty) – 6 cases and Group B (failure with Titanium mesh) – 2 cases. Out of this, 1 case had undergone cranioplasty using Titanium mesh plus bone cement and failure was attributed to extrusion of bone cement. Thus, statistically speaking, the complication rate of Group A (PMMA cranioplasty) was 42.85% (6 out of 14) and of Group B (Titanium cranioplasty) was 14.28%. Statistics of Group B can be further subdivided into 7.14% (1 case) when Titanium mesh was exclusively used and 7.14% (1 case) when Titanium mesh had been used in combination with bone cement.

Chi square test analysis applied to Group A and Group B revealed Chi square statistic of 6.0921 with p-value of .013 (statistically significant). Further, Chi square statistic with Yates correction was calculated at 4.3222 with p-value of .037 (also statistically significant).

Causes of failure were - infection 05 cases, flap breakdown 02, lack of fixation 04, poor fitting of implant 01, foreign body 01 and recurrence of brain tumor in 01 case (Table −1). Successful reconstruction for the second time was carried out in 08 cases where as 06 cases could not be operated.

5. Discussion

The purpose of cranioplasty is to restore the function (protection of the brain) and form (esthetic appearance) of the skull. Biomaterials used for cranioplasty has undergone a long evolution. From the Egyptians and Incans use of gold plates to the current era of 3-D printed patient specific implants made of modern, synthetic and inert materials.^{1, 2, 3, 4}

Reconstruction of residual calvarial defect is challenging due to factors like etiology, existing pathology, condition of flap, size and site of defect, associated co-morbidity and availability of reconstruction material.

Failure has a serious and adverse impact on the patient besides the financial burden. Repeated reconstruction may not be feasible technically.

Persistent pain, fluctuant fluid collection at the operative site and fever are the features of infection which leads to early failure within one to two weeks after reconstruction. Flap breakdown, persistent or recurrent draining sinus, exposure of reconstruction material [Fig. 1(a,b,c)] due to insufficient soft tissue coverage or radiation therapy over the surgical site may occur at a later stage which may be associated with delayed or late failure. Effort should be made to identify whether the root cause of failure is a local or systemic factor.

Fig. 1.

(a,b,c) Presenting features of delayed/late failure.

Preoperative surgical part preparation plays an important role in avoiding infection post operatively. The patient’s apprehension to touch and clean the skin over the surgical site leads to collection of dust, crusting, fungal infection and folliculitis. Head shaving a week before surgery, daily head bath with antibacterial shampoo/antiseptic solution and topical application of antiseptic cream help in keeping the scalp defect site clean preoperatively. The head is again shaved a day before surgery.

While exposing a cranial defect of the frontal bone, communication with frontal sinus should be avoided. If reconstruction material is placed in communication with the frontal sinus, there is a chance of infection of the reconstruction material resulting in failure. In one of the cases in which bone cement and titanium mesh was used in combination, communication with the frontal sinus resulted in lumping of the bone cement and infection (Fig. 2).

Fig. 2.

Lumping of bone cement and infection.

On completion of surgery the surgical field is inspected for any foreign body and irrigated with sterile saline and betadine solution. The vacuum drain tubing is kept away from the suture line. Subcutaneous use of poly filamentous suture material should be minimal. Pressure dressing is left in situ for 72 ​h. Local wound dressing and parenteral administration of culture sensitive antibiotics for adequate duration are crucial. Medical consultation should be done for management of any existing co-morbidity. MRI is done to ascertain spread of infection if required.

Current literature reports a median removal rate of 10.4% (ranging from 0 to 50%) for autologous bone flaps and 5.1% for combined alloplastic cranioplasties.⁵ In our study, six cases of failure were due to poor implant fabrication and surgical execution and were avoidable. Poor fitting of the implant is avoidable with the use of CAD- CAM technology and construction of patient specific implants. However, a study by Williams et al., in 2015 on cranioplasty with custom fabricated titanium implants reported an overall late complication rate of 19%.⁶ In their series, six of the 149 patients developed late infection requiring removal of the cranial plate.

Cheng et al., in 2008 reported a 6.25% failure rate with PMMA cranioplasty,⁷ which was similar to Akan et al.’s reported failure rate of 6% rate with PMMA.⁸

When titanium mesh is used, customization and adaptation is done directly over the defect. The adaptation should be as passive as possible with the help of a 3D bender. The cut ends are bent towards the bone to avoid “cactus effect”. In oval defects “V" shaped wedges should be removed from the margin to avoid kinking of the mesh. Alloplastic implant is not a suitable option for young patients as the fitting is altered in due course of time due to calvarial growth and remodeling. In one case of poor fitting, primary cranioplasty was done using self cure PMMA at the age of seven years. At the age of 18 years the patient reported with a complaint of palpable implant which was replaced with CAD CAM designed titanium implant. In spite of the fact that the self cure PMMA was in situ for 11 years without any fixation, the implant was stable due to adaptation with irregular bony margins and there was no tissue necrosis or infection. Stable fixation of biomaterial should always be carried out to hold it in position during healing, to ensure early and long term stability and to avoid extrusion. We use at least three point fixation for single piece alloplastic implant distributed more than two third of its perimeter for better stability. Fibrous tissue in-growth through the holes takes place within after 5–7 days which helps in stability. Movement of the implant during early stage induces mechanical trauma which is detrimental to healing and hampers the growth of fibrous tissue. Same principle of fixation is also applicable to single piece of bone flap. Multiple bur holes are done in bone flap under sterile saline coolant to prevent thermal necrosis. Bur hole or sieving helps to prevent any collection under the bone flap and promotes revascularization for better osteoinduction and osteoconduction. When multiple strips of bone graft are used, each strip should be stabilized.

Blum et al., in 1997 had 17 cases (23%) of failed cranioplasties with PMMA requiring removal. Of these, 12 were due to infection, 3 dislodgements and 2 implant fractures.⁹

Preserved calvarial (craniectomy) bone flap has always been a preferred cranioplasty option where available. However, this modality too has been associated with failures. Matsuno et al., in 2006 in a series of 54 preserved bone flap cranioplasties where cryo preservation followed by autoclaving of the bone flap had been carried out, reported an infection rate of 25.9% resulting in failure and subsequent graft removal.¹⁰ The preserved bone flap also has a tendency to undergo resorption, resulting in short margins and poor fitting of the cranioplasty bone flap. Grant et al., in 2004 reported resorption of bone flap requiring removal and reoperation in 50% in their series of 40 pediatric cranioplasty with a cryopreserved bone flap.¹¹ Whereas, Gooch et al. later in 2009 reported resorption of the preserved bone flap requiring a second cranioplasty in 26% cases amongst a series of 57 preserved bone flap cranioplasties.¹²

Customized implants are supplied pre sterilized by the manufacturers. If required the metallic implants can be sterilized in-house by autoclaving. For cold sterilization of the PMMA implant, it should be submersed in sterilizing solution for a stipulated period as directed by the manufacturer.

Co-relation between failure and the type of biomaterial used for reconstruction has been documented, as is consistent with our study as well.^{13, 14, 15, 16} When using alloplast material (PMMA and Titanium mesh), statistical significance was observed in comparison of failure rate between PMMA (Group A) and Titanium mesh (Group B) with p-value of .013 in Chi square analysis and p-value of .037 in Chi square analysis with Yates correction.

In the patient of second time failure, first cranioplasty had been done with preserved bone flap and in second cranioplasty PMMA plate had been used. Both reconstruction modalities had failed. Third cranioplasty procedure had then not been carried out.

There is no definite time frame when to remove the reconstruction material. Patients have reported even one year after having exposed implant and draining sinus. Regardless of the cause and duration of failure the only treatment option is to remove the reconstruction material. The sooner it is removed, the better is the healing and further consideration for reconstruction.

After removal of reconstruction material adequate time is required for healing and consideration for second reconstruction. We considered the cases at least six months after removal of reconstruction material. Systemic condition if any are managed. The defect site should be free from disease.

Out of 14 cases, 8 were successfully re-operated. Remaining 6 cases could not be re-operated.

The 8 cases successfully operated were reconstructed with varying reconstruction materials. We used titanium mesh in 4 cases, customized single piece titanium implant in 2, bone graft in 1 and combination of bone graft and titanium mesh in 1 patient for reconstruction. The remaining 6 cases that couldn’t be operated included 2 cases of flap break down, 2 with poor systemic condition, 1 with a recurrence of brain tumor and 1 case of second time failure. One case of flap break down was due to pre-reconstruction radiotherapy and closure of soft tissue using pedicle flap. In the second case the loss of scalp tissue was repaired with split skin graft which got necrosed.

A fair audit of these failed cranioplasty cases would indicate that soft tissue flap necrosis and recurrence of tumor are factors beyond the control of the operating surgeon. However, factors which are under the operator’s control are lack of fixation and poor fitting of implant. These could be avoided and thus 5 cases could be held attributable to the operators surgical planning and execution. These factors (inadequate fixation and poor fitting implants) could serve as reference points for further research in cranial reconstruction.

The strength of this study is the inclusion of different reconstruction materials for cranioplasty as failure cases, reasonable sample size and also fairness of attributing operator’s factors in causes for failure. Further, laying down suggestions for time frames that can be adopted for re-do procedures adds to the study’s strengths.

A limitation of the study is that follow up period could have been longer.

6. Conclusion

Cranioplasty has always been a technique sensitive, operator skill dependent and demanding surgical procedure. In order to provide optimum results and minimize the chance of failure, several factors such as systemic condition of the patient, status of the cranial surgical site, etiology behind craniectomy, choice of reconstruction material, duration from craniectomy and age of the patient need to taken into consideration. Even with ideal preparation and planning, certain etiological factors of failure are beyond the control of the operator.

Funding source

Nil.

Ethical approval

Taken from institutional ethical committee.

Declaration of competing interest

None declared.