Cranioplasty with hydroxyapatite or acrylic is associated with a reduced risk of all-cause and infection-associated explantation

Figures & data

Table 1. Craniectomy details.

Variable	Sub-variable	Total number (%)
Number of patients		287
Mean age in years [SD]		42.9 [15.4]
Sex	Male	183 (63.8)
	Female	104 (36.2)
Indication for craniectomy	Traumatic brain injury	92 (32.1)
	Tumour (any pathology)	68 (23.7)
	Infected bone flap	53 (18.5)
	Cerebral infarct	23 (8)
	Intracerebral haemorrhage	13 (4.5)
	Subarachnoid haemorrhage	11 (3.8)
	Cystic lesion	9 (3.1)
	Primary intracranial infection	5 (1.7)
	Other	13 (4.5)
Operative details
Urgency of surgery	Elective	128 (44.6)
	Urgent	152 (53)
	Unknown	7 (2.4)
Craniectomy site	Right hemispheric	78 (27.2)
	Left hemispheric	65 (22.6)
	Right hemicraniectomy	52 (18.1)
	Left hemicraniectomy	41 (14.3)
	Bifrontal	27 (9.4)
	Occipital	7 (2.4)
	Left retrosigmoid	1 (0.3)
	Midline/Vertex	1 (0.3)
	Unknown	15 (5.2)
Duroplasty use	Yes	77 (26.8)
	No	187 (65.2)
	Unknown	23 (8)
Duroplasty material	TissuDura	28 (9.8)
	Spongostan	14 (4.9)
	DuraGen	13 (4.5)
	Resodura	6 (2.1)
	Unknown	16 (5.6)
Closure technique	Monofilament	214 (74.6)
	Clips	49 (17.1)
	Unknown	24 (8.4)

Demographics, baseline characteristics and operative details for the cohort at the time of craniectomy. With respect to indication for craniectomy, tumour includes both benign and malignant lesions whereby craniectomy is not secondary to infection, whereas infected bone flap includes those patients who have undergone craniotomy and subsequently required craniectomy to manage the infection, primary intracranial infection includes both subdural empyema and abscess.

Table 2. Cranioplasty details.

Variable	Sub-variable	Total number (%)
Mean age in years [SD]		44.1 [15.2]
Median ACCI [Range]		0 [0–9]
ASA	I	158 (55.1)
	II	108 (37.6)
	III	17 (5.9)
	IV	2 (0.7)
	Unknown	2 (0.7)
Smoking status	Yes	65 (22.6)
	No	216 (75.3)
	Unknown	6 (2.1)
Time to cranioplasty	Median time in months [IQR]	7 [1-15]
	Primary ‘on-table’ cranioplasty	69 (24)
	Less than 3 months	12 (4.2)
	3–6 months	36 (12.5)
	6–12 months	69 (24)
	Over 12 months	101 (35.2)
Cranioplasty material	Titanium plate	67 (23.3)
	Hydroxyapatite	64 (22.3)
	Acrylic	59 (20.6)
	Titanium mesh	55 (19.2)
	Hand-moulded PMMA	26 (9.1)
	PEEK	16 (5.6)
Seniority of surgeon/s	Only junior/trainee	66 (23)
	Senior surgeon present	198 (69)
	Two senior surgeons present	18 (6.3)
	Unknown	5 (1.7)
Cranioplasty soaked in ABX	Total	24 (8.4)
	Soaked in gentamicin	12 (4.2)
	Soaked in vancomycin	12 (4.2)
	Not soaked/no reference to event	263 (91.6)
Drain usage	Yes	68 (23.7)
	No	214 (74.6)
	Unknown	5 (1.7)
CSF diversion	New shunt	3 (1.0)
	Lumbar drain	2 (0.7)
	Shunt in situ	1 (0.3)
	External ventricular drain	1 (0.3)
	No CSF diversion	275 (95.8)
	Unknown	5 (1.7)
Closure technique	Monofilament	248 (86.4)
	Clips	34 (11.8)
	Unknown	5 (1.7)

Demographics, baseline characteristics and operative details for patients undergoing first cranioplasty between 1 January 2010 and 1 September 2021 at The Walton Centre NHS Foundation Trust.

Table 3. Morbidity and mortality.

Variable	Sub-variable	Total number (%)
Total No. of patients with a complication		97 of 287 (33.8)
Mean age in years of patients with complication/s [SD]		46.4 [15.6]
Median follow-up time in months after cranioplasty [IQR]		86.5 [44.6–111.3]
Median ACCI of patients with complication/s [Range]		1 [0–5]
No. of complication/s	1	79 of 287 (29.2)
	2	15 of 287 (5.5)
	3 or more	4 of 287 (1.5)
Type of complication/s	Had a surgical complication	83 of 287 (28.9)
	Had a neurological complication	16 of 287 (5.6)
	Had a medical complication	4 of 287 (1.5)
Total no. and no. of specific surgical complications	Total No. complications	120
	Total No. surgical complications	98 (81.7)
	Any infection	41 of 98 (41.8)
	CSF complications	26 of 98 (26.5)
	Extra-axial haematoma	14 of 98 (14.3)
	Wound complications	11 of 98 (11.2)
	Cosmetic complaint	6 of 98 (6.1)
Total no. of patients who had further surgery		57 of 287 (19.9)
Reason for further surgery	Explantation due to infection	27 of 287 (9.4)
	Explantation not due to infection	8 of 287 (2.8)
	Other surgery	22 of 287 (7.7)
Mortality	Total mortality at follow-up	43 (15.0)
	Within 30 days	3 (1.0)

Demographics, baseline characteristics, morbidity counts, further surgery frequencies and mortality for patients undergoing first cranioplasty between 1 January 2010 and 1 September 2021 at The Walton Centre NHS Foundation Trust, Liverpool, UK.

Table 4. Morbidity stratified by cranioplasty material.

Alloplastic material no. cases	All-cause explantation no. cases (% within material)	Explantation due to infection no. cases (% within material)	Any surgical morbidity no. cases (% within material)
Titanium plate (n = 67)	15 (22.4)	12 (17.9)	23 (34.3)
Hydroxyapatite (n = 64)	4 (6.3)	3 (4.7)	16 (25)
Acrylic (n = 59)	3 (5.1)	3 (5.1)	13 (22.0)
Titanium mesh (n = 55)	8 (14.5)	5 (9.1)	18 (32.7)
Hand-moulded PMMA (n = 26)	2 (7.7)	1 (3.8)	7 (26.9)
PEEK (n = 16)	3 (18.8)	3 (18.8)	6 (37.5)
Entire cohort (n = 287)	35 (12.2%)	27 (9.4)	83 (28.9)

Cases of explantation, explantation due to infection and number of patients experiencing any surgical morbidity event stratified by cranioplasty material. Percentages are calculated to demonstrate the proportion of each event for each material; for instance 15 titanium plates were explanted for any reason out of a total of 67 inserted (22.4%). Overall summary figures are provided at the bottom of the table, with percentages representing the proportion of the total cohort.

Figure 1. Classification of surgical morbidity. Frequency of patients with each Therapy-Disability-Neurology (TDN) grade, stratified by cranioplasty material which (A) occurred within 30 days and resolved, (B) occurred within 30 days and persisted, (C) occurred after 30 days and (D) for all patients both with and without surgical morbidity events, at any time. The surgical morbidity event that produced the highest grade was ultimately used for grading whee more than one event occurred in a particular patient. Grade 5 events (death) appear in Panel B as they are within 30 days and cannot resolve. The number at the top of each stacked bar states the total number of patients with a surgical morbidity event, within that timeframe. The number in association with each material on the x-axis states the frequency of insertion of that material in total.

Figure 2. Explantation and mortality. Kaplan–Meier curves demonstrating (A) all-cause explantation free survival, (B) explantation due to infection free survival and (C) overall survival following cranioplasty. Shaded area indicates the 95% CI.